On 11/14/23 10:04, Jiri Slaby wrote: > On 14. 11. 23, 16:12, Tomas Mudrunka wrote: >> Just for convenience. >> This way we can do: >> `echo _reisub > /proc/sysrq-trigger` >> Instead of: >> `for i in r e i s u b; do echo "$i" > /proc/sysrq-trigger; done;` >> >> This can be very useful when trying to execute sysrq combo remotely >> or from userspace. When sending keys in multiple separate writes, >> userspace can be killed before whole combo is completed. >> Therefore putting all keys in single write is more robust approach. >> >> Signed-off-by: Tomas Mudrunka <tomas.mudrunka@xxxxxxxxx> >> --- >> V5 -> V6: Documentation now has notice about undefined behavior >> V4 -> V5: Added this list of changes >> V3 -> V4: Bulk is now bool instead of char (and fixed typo) >> V2 -> V3: Fixed code styling (and introduced typo) >> V1 -> V2: Bulk mode only activated by underscore now, added docs >> >> Documentation/admin-guide/sysrq.rst | 11 ++++++++++- >> drivers/tty/sysrq.c | 17 ++++++++++++++--- >> 2 files changed, 24 insertions(+), 4 deletions(-) >> >> diff --git a/Documentation/admin-guide/sysrq.rst b/Documentation/admin-guide/sysrq.rst >> index 51906e473..e7a82cba7 100644 >> --- a/Documentation/admin-guide/sysrq.rst >> +++ b/Documentation/admin-guide/sysrq.rst >> @@ -75,10 +75,19 @@ On other >> submit a patch to be included in this section. >> On all >> - Write a character to /proc/sysrq-trigger. e.g.:: >> + Write single character to /proc/sysrq-trigger. > > a single > >> + Only first character is interpreted, rest of string is ignored. > > the first; the rest of the string > >> + However it is not reccomended to write any extra characters > > However, <- comma > recommended > >> + as the behavior is undefined and might change in the future versions. >> + e.g.:: > > Even the original was lowercase. But it should be "E.g.::", right -- Greg/Jon? > or Randy? Yes, you are correct. All of your recommendations look good. Thanks. >> echo t > /proc/sysrq-trigger >> + Alternatively write multiple keys combo prepended by underscore. > > Alternatively, <- comma > s/keys/characters/ > an underscore > >> + All characters are interpreted this way. e.g.:: > > This way, all characters are interpreted. (IMO this has a different meaning, but natives would have to tell us.) > >> + >> + echo _reisub > /proc/sysrq-trigger >> + >> The :kbd:`<command key>` is case sensitive. >> What are the 'command' keys? >> diff --git a/drivers/tty/sysrq.c b/drivers/tty/sysrq.c >> index 6b4a28bcf..ad07bc812 100644 >> --- a/drivers/tty/sysrq.c >> +++ b/drivers/tty/sysrq.c >> @@ -1150,16 +1150,27 @@ EXPORT_SYMBOL(unregister_sysrq_key); >> #ifdef CONFIG_PROC_FS >> /* >> * writing 'C' to /proc/sysrq-trigger is like sysrq-C >> + * If first character in write is underscore, all characters are interpreted. > > If the first character written is > > thanks, -- ~Randy
