Messages in this thread | | | Subject | Re: [PATCH] powercap: Adjust printing the constraint name with new line | From | Lukasz Luba <> | Date | Tue, 17 Nov 2020 12:57:10 +0000 |
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On 11/17/20 12:51 PM, Rafael J. Wysocki wrote: > On Tue, Nov 17, 2020 at 10:22 AM Lukasz Luba <lukasz.luba@arm.com> wrote: >> >> Hi Rafael, >> >> On 11/10/20 7:19 PM, Rafael J. Wysocki wrote: >>> On Mon, Nov 9, 2020 at 6:25 PM Lukasz Luba <lukasz.luba@arm.com> wrote: >>>> >>>> The constraint name has limit of size 30, which sometimes might be hit. >>>> When this happens the new line might be lost. Prevent this and set the >>>> new line when the name string is too long." >>>> >>>> Signed-off-by: Lukasz Luba <lukasz.luba@arm.com> >>>> --- >>>> drivers/powercap/powercap_sys.c | 4 ++++ >>>> 1 file changed, 4 insertions(+) >>>> >>>> diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c >>>> index f808c5fa9838..575f9fdb810e 100644 >>>> --- a/drivers/powercap/powercap_sys.c >>>> +++ b/drivers/powercap/powercap_sys.c >>>> @@ -174,6 +174,10 @@ static ssize_t show_constraint_name(struct device *dev, >>>> "%s\n", name); >>>> buf[POWERCAP_CONSTRAINT_NAME_LEN] = '\0'; >>>> len = strlen(buf); >>>> + >>>> + /* When the 'name' is too long, don't lose new line */ >>>> + if (strlen(name) >= POWERCAP_CONSTRAINT_NAME_LEN) >>>> + buf[POWERCAP_CONSTRAINT_NAME_LEN - 1] = '\n'; >>> >>> Wouldn't it be better to pass POWERCAP_CONSTRAINT_NAME_LEN - 1 to >>> snprintf() above? >> >> My apologies for delay, I was on holidays. >> >> The snprintf() overwrites the '\n' in that case also. > > The snprintf() doesn't do that AFAICS, but the next assignment > overwrites the newline with the zero character. > > Anyway, it should have been POWERCAP_CONSTRAINT_NAME_LEN - 2, because > it needs to leave space for 2 characters, the newline and the > terminating zero. > >> I've experimented with it a bit more and tried to come with a bit 'cleaner' solution. >> >> What we are looking is probably: "%.*s\n" semantic. >> Another solution would be: >> ------------------------------8<--------------------------- >> if (name) { >> - snprintf(buf, POWERCAP_CONSTRAINT_NAME_LEN, >> - "%s\n", >> name); >> - buf[POWERCAP_CONSTRAINT_NAME_LEN] = '\0'; >> + sprintf(buf, "%.*s\n", >> POWERCAP_CONSTRAINT_NAME_LEN -1, >> + name); >> len = strlen(buf); >> } >> >> ----------------------------->8---------------------------- >> >> I've check this and it behaves very well. >> >> It looks cleaner and it is a used pattern in the kernel. >> What do you think? Is it good for v2? > > This works for me too. > > Thanks! >
Thank you for the comments. I will send the v2 then.
Regards, Lukasz
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