printk: Rename console_start to console_resume

The intent of console_start was to resume a previously suspended console,
so rename it accordingly.

Signed-off-by: Marcos Paulo de Souza <mpdesouza@su

printk: Rename console_start to console_resume

The intent of console_start was to resume a previously suspended console,
so rename it accordingly.

Signed-off-by: Marcos Paulo de Souza <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Reviewed-by: John Ogness <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: Fixed typo in the commit message. Updated also new drm_log.c.]
Signed-off-by: Petr Mladek <[email protected]>

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printk: Rename console_stop to console_suspend

The intent of console_stop was in fact to suspend it, so rename the
function accordingly.

Signed-off-by: Marcos Paulo de Souza <[email protected]>
Re

printk: Rename console_stop to console_suspend

The intent of console_stop was in fact to suspend it, so rename the
function accordingly.

Signed-off-by: Marcos Paulo de Souza <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Reviewed-by: John Ogness <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: Fixed typo in the commit message. Updated also new drm_log.c]
Signed-off-by: Petr Mladek <[email protected]>

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printk: Rename resume_console to console_resume_all

The function resume_console has a misleading name, since it resumes all
consoles, so rename it accordingly.

Signed-off-by: Marcos Paulo de Souza

printk: Rename resume_console to console_resume_all

The function resume_console has a misleading name, since it resumes all
consoles, so rename it accordingly.

Signed-off-by: Marcos Paulo de Souza <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Reviewed-by: John Ogness <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: Fixed typo in the commit message.]
Signed-off-by: Petr Mladek <[email protected]>

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printk: Rename suspend_console to console_suspend_all

The function suspend_console has a misleading name, since it suspends all
consoles, so rename it accordingly.

Signed-off-by: Marcos Paulo de So

printk: Rename suspend_console to console_suspend_all

The function suspend_console has a misleading name, since it suspends all
consoles, so rename it accordingly.

Signed-off-by: Marcos Paulo de Souza <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Reviewed-by: John Ogness <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[[email protected]: Fixed typo in the commit message.]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Show replay message on takeover

An emergency or panic context can takeover console ownership
while the current owner was printing a printk message. The
atomic printer will re-print th

printk: nbcon: Show replay message on takeover

An emergency or panic context can takeover console ownership
while the current owner was printing a printk message. The
atomic printer will re-print the message that the previous
owner was printing. However, this can look confusing to the
user and may even seem as though a message was lost.

[3430014.1
[3430014.181123] usb 1-2: Product: USB Audio

Add a new field @nbcon_prev_seq to struct console to track
the sequence number to print that was assigned to the previous
console owner. If this matches the sequence number to print
that the current owner is assigned, then a takeover must have
occurred. In this case, print an additional message to inform
the user that the previous message is being printed again.

[3430014.1
** replaying previous printk message **
[3430014.181123] usb 1-2: Product: USB Audio

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Introduce printer kthreads

Provide the main implementation for running a printer kthread
per nbcon console that is takeover/handover aware. This
includes:

- new mandatory write_threa

printk: nbcon: Introduce printer kthreads

Provide the main implementation for running a printer kthread
per nbcon console that is takeover/handover aware. This
includes:

- new mandatory write_thread() callback
- kthread creation
- kthread main printing loop
- kthread wakeup mechanism
- kthread shutdown

kthread creation is a bit tricky because consoles may register
before kthreads can be created. In such cases, registration
will succeed, even though no kthread exists. Once kthreads can
be created, an early_initcall will set @printk_kthreads_ready.
If there are no registered boot consoles, the early_initcall
creates the kthreads for all registered nbcon consoles. If
kthread creation fails, the related console is unregistered.

If there are registered boot consoles when
@printk_kthreads_ready is set, no kthreads are created until
the final boot console unregisters.

Once kthread creation finally occurs, @printk_kthreads_running
is set so that the system knows kthreads are available for all
registered nbcon consoles.

If @printk_kthreads_running is already set when the console
is registering, the kthread is created during registration. If
kthread creation fails, the registration will fail.

Until @printk_kthreads_running is set, console printing occurs
directly via the console_lock.

kthread shutdown on system shutdown/reboot is necessary to
ensure the printer kthreads finish their printing so that the
system can cleanly transition back to direct printing via the
console_lock in order to reliably push out the final
shutdown/reboot messages. @printk_kthreads_running is cleared
before shutting down the individual kthreads.

The kthread uses a new mandatory write_thread() callback that
is called with both device_lock() and the console context
acquired.

The console ownership handling is necessary for synchronization
against write_atomic() which is synchronized only via the
console context ownership.

The device_lock() serializes acquiring the console context with
NBCON_PRIO_NORMAL. It is needed in case the device_lock() does
not disable preemption. It prevents the following race:

CPU0 CPU1

[ task A ]

nbcon_context_try_acquire()
# success with NORMAL prio
# .unsafe == false; // safe for takeover

[ schedule: task A -> B ]

WARN_ON()
nbcon_atomic_flush_pending()
nbcon_context_try_acquire()
# success with EMERGENCY prio

# flushing
nbcon_context_release()

# HERE: con->nbcon_state is free
# to take by anyone !!!

nbcon_context_try_acquire()
# success with NORMAL prio [ task B ]

[ schedule: task B -> A ]

nbcon_enter_unsafe()
nbcon_context_can_proceed()

BUG: nbcon_context_can_proceed() returns "true" because
the console is owned by a context on CPU0 with
NBCON_PRIO_NORMAL.

But it should return "false". The console is owned
by a context from task B and we do the check
in a context from task A.

Note that with these changes, the printer kthreads do not yet
take over full responsibility for nbcon printing during normal
operation. These changes only focus on the lifecycle of the
kthreads.

Co-developed-by: John Ogness <[email protected]>
Signed-off-by: John Ogness <[email protected]>
Signed-off-by: Thomas Gleixner (Intel) <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Add function for printers to reacquire ownership

Since ownership can be lost at any time due to handover or
takeover, a printing context _must_ be prepared to back out
immediately and

printk: nbcon: Add function for printers to reacquire ownership

Since ownership can be lost at any time due to handover or
takeover, a printing context _must_ be prepared to back out
immediately and carefully. However, there are scenarios where
the printing context must reacquire ownership in order to
finalize or revert hardware changes.

One such example is when interrupts are disabled during
printing. No other context will automagically re-enable the
interrupts. For this case, the disabling context _must_
reacquire nbcon ownership so that it can re-enable the
interrupts.

Provide nbcon_reacquire_nobuf() for exactly this purpose. It
allows a printing context to reacquire ownership using the same
priority as its previous ownership.

Note that after a successful reacquire the printing context
will have no output buffer because that has been lost. This
function cannot be used to resume printing.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Implement emergency sections

In emergency situations (something has gone wrong but the
system continues to operate), usually important information
(such as a backtrace) is generated v

printk: nbcon: Implement emergency sections

In emergency situations (something has gone wrong but the
system continues to operate), usually important information
(such as a backtrace) is generated via printk(). This
information should be pushed out to the consoles ASAP.

Add per-CPU emergency nesting tracking because an emergency
can arise while in an emergency situation.

Add functions to mark the beginning and end of emergency
sections where the urgent messages are generated.

Perform direct console flushing at the emergency priority if
the current CPU is in an emergency state and it is safe to do
so.

Note that the emergency state is not system-wide. While one CPU
is in an emergency state, another CPU may attempt to print
console messages at normal priority.

Also note that printk() already attempts to flush consoles in
the caller context for normal priority. However, follow-up
changes will introduce printing kthreads, in which case the
normal priority printk() calls will offload to the kthreads.

Co-developed-by: John Ogness <[email protected]>
Signed-off-by: John Ogness <[email protected]>
Signed-off-by: Thomas Gleixner (Intel) <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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nbcon: Add API to acquire context for non-printing operations

Provide functions nbcon_device_try_acquire() and
nbcon_device_release() which will try to acquire the nbcon
console ownership with NBCON

nbcon: Add API to acquire context for non-printing operations

Provide functions nbcon_device_try_acquire() and
nbcon_device_release() which will try to acquire the nbcon
console ownership with NBCON_PRIO_NORMAL and mark it unsafe for
handover/takeover.

These functions are to be used together with the device-specific
locking when performing non-printing activities on the console
device. They will allow synchronization against the
atomic_write() callback which will be serialized, for higher
priority contexts, only by acquiring the console context
ownership.

Pitfalls:

The API requires to be called in a context with migration
disabled because it uses per-CPU variables internally.

The context is set unsafe for a takeover all the time. It
guarantees full serialization against any atomic_write() caller
except for the final flush in panic() which might try an unsafe
takeover.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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console: Improve console_srcu_read_flags() comments

It was not clear when exactly console_srcu_read_flags() must be
used vs. directly reading @console->flags.

Refactor and clarify that console_srcu

console: Improve console_srcu_read_flags() comments

It was not clear when exactly console_srcu_read_flags() must be
used vs. directly reading @console->flags.

Refactor and clarify that console_srcu_read_flags() is only
needed if the console is registered or the caller is in a
context where the registration status of the console may change
(due to another context).

The function requires the caller holds @console_srcu, which will
ensure that the caller sees an appropriate @flags value for the
registered console and that exit/cleanup routines will not run
if the console is in the process of unregistration.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Add callbacks to synchronize with driver

Console drivers typically must deal with access to the hardware
via user input/output (such as an interactive login shell) and
output of kerne

printk: nbcon: Add callbacks to synchronize with driver

Console drivers typically must deal with access to the hardware
via user input/output (such as an interactive login shell) and
output of kernel messages via printk() calls. To provide the
necessary synchronization, usually some driver-specific locking
mechanism is used (for example, the port spinlock for uart
serial consoles).

Until now, usage of this driver-specific locking has been hidden
from the printk-subsystem and implemented within the various
console callbacks. However, nbcon consoles would need to use it
even in the generic code.

Add device_lock() and device_unlock() callback which will need
to get implemented by nbcon consoles.

The callbacks will use whatever synchronization mechanism the
driver is using for itself. The minimum requirement is to
prevent CPU migration. It would allow a context friendly
acquiring of nbcon console ownership in non-emergency and
non-panic context.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Add detailed doc for write_atomic()

The write_atomic() callback has special requirements and is
allowed to use special helper functions. Provide detailed
documentation of the callback

printk: nbcon: Add detailed doc for write_atomic()

The write_atomic() callback has special requirements and is
allowed to use special helper functions. Provide detailed
documentation of the callback so that a developer has a
chance of implementing it correctly.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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printk: nbcon: Remove return value for write_atomic()

The return value of write_atomic() does not provide any useful
information. On the contrary, it makes things more complicated
for the caller to

printk: nbcon: Remove return value for write_atomic()

The return value of write_atomic() does not provide any useful
information. On the contrary, it makes things more complicated
for the caller to appropriately deal with the information.

Change write_atomic() to not have a return value. If the
message did not get printed due to loss of ownership, the
caller will notice this on its own. If ownership was not lost,
it will be assumed that the driver successfully printed the
message and the sequence number for that console will be
incremented.

Signed-off-by: John Ogness <[email protected]>
Reviewed-by: Petr Mladek <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Petr Mladek <[email protected]>

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vt: remove superfluous CONFIG_HW_CONSOLE

The config HW_CONSOLE is always identical to the config VT and is not
visible in the kernel's build menuconfig. So, CONFIG_HW_CONSOLE is
redundant.

Replace

vt: remove superfluous CONFIG_HW_CONSOLE

The config HW_CONSOLE is always identical to the config VT and is not
visible in the kernel's build menuconfig. So, CONFIG_HW_CONSOLE is
redundant.

Replace all references to CONFIG_HW_CONSOLE with CONFIG_VT and remove
CONFIG_HW_CONSOLE.

Signed-off-by: Lukas Bulwahn <[email protected]>
Reviewed-by: Javier Martinez Canillas <[email protected]>
Acked-by: Dmitry Torokhov <[email protected]>
Reviewed-by: Geert Uytterhoeven <[email protected]>
Acked-by: Geert Uytterhoeven <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: fix up kernel-doc

selection.c and vt.c still uses tabs in the kernel-doc. This misrenders the
functions in the output -- sphinx misinterprets the description. So
remove these tabs, incl. th

tty: vt: fix up kernel-doc

selection.c and vt.c still uses tabs in the kernel-doc. This misrenders the
functions in the output -- sphinx misinterprets the description. So
remove these tabs, incl. those around dashes.

'enum' keyword is needed before enum names. Fix that.

Superfluous \n after the comments are also removed. They are not
completely faulty, but this unifies all the kernel-doc in the files.

Finally fix up the cross references.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Reviewed-by: Randy Dunlap <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: document the rest of struct consw

There are still members of struct consw which are not documented yet.
Fix that up, so we can generate kernel-doc for that struct.

Signed-off-by: "Jiri Sla

tty: vt: document the rest of struct consw

There are still members of struct consw which are not documented yet.
Fix that up, so we can generate kernel-doc for that struct.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: remove unused consw::con_flush_scrollback()

consw::con_flush_scrollback() is unused since commit 973c096f6a85
(vgacon: remove software scrollback support). Drop it.

Signed-off-by: "Jiri Sl

tty: vt: remove unused consw::con_flush_scrollback()

consw::con_flush_scrollback() is unused since commit 973c096f6a85
(vgacon: remove software scrollback support). Drop it.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: remove consw::con_getxy()

After the previous patch, nobody sets that hook. So drop it completely.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <deller@

tty: vt: remove consw::con_getxy()

After the previous patch, nobody sets that hook. So drop it completely.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: remove consw::con_screen_pos()

After the previous patch, nobody sets that hook. So drop it completely.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <de

tty: vt: remove consw::con_screen_pos()

After the previous patch, nobody sets that hook. So drop it completely.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: change consw::con_set_origin() return type

The return value of consw::con_set_origin() is only true/false, meaining
if vc->vc_origin is set to vc->vc_screenbuf or not.

So switch the type a

tty: vt: change consw::con_set_origin() return type

The return value of consw::con_set_origin() is only true/false, meaining
if vc->vc_origin is set to vc->vc_screenbuf or not.

So switch the type and returned values accordingly.

And document the hook.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: [email protected]
Cc: [email protected]
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: make consw::con_font_default()'s name const

It's a name after all and that is not supposed to be changed. So make it
const to make this obvious.

Signed-off-by: "Jiri Slaby (SUSE)" <jirisla

tty: vt: make consw::con_font_default()'s name const

It's a name after all and that is not supposed to be changed. So make it
const to make this obvious.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: make font of consw::con_font_set() const

Provided the font parameter of consw::con_font_set() is not supposed to
be changed, make it const.

Signed-off-by: "Jiri Slaby (SUSE)" <jirislaby@ke

tty: vt: make font of consw::con_font_set() const

Provided the font parameter of consw::con_font_set() is not supposed to
be changed, make it const.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: make types around consw::con_blank() bool

Both the mode_switch parameter and the return value (a redraw needed)
are true/false. So switch them to bool, so that users won't return
-Eerrors o

tty: vt: make types around consw::con_blank() bool

Both the mode_switch parameter and the return value (a redraw needed)
are true/false. So switch them to bool, so that users won't return
-Eerrors or anything else.

And document the hook.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: use enum constants for VESA blanking modes

Use the new enum for VESA constants. This improves type checking in
consw::con_blank().

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>

tty: vt: use enum constants for VESA blanking modes

Use the new enum for VESA constants. This improves type checking in
consw::con_blank().

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: "James E.J. Bottomley" <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

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tty: vt: define a common enum for VESA blanking constants

There are currently two places with VESA blanking constants definitions:
fb.h and console.h. Extract/unify the two to a separate header (ves

tty: vt: define a common enum for VESA blanking constants

There are currently two places with VESA blanking constants definitions:
fb.h and console.h. Extract/unify the two to a separate header (vesa.h).

Given the fb's is in an uapi header, create the common header in uapi
too.

Note that instead of macros, an enum (vesa_blank_mode) is created. But
the macros are kept too (they now expand to the enum constants), just in
case someone in userspace performs some #ifdeffery.

Signed-off-by: "Jiri Slaby (SUSE)" <[email protected]>
Cc: Helge Deller <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Cc: Thomas Zimmermann <[email protected]>
Tested-by: Helge Deller <[email protected]> # parisc STI console
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

show more ...