From: Kent Gibson <warthog618@gmail.com>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"open list:GPIO SUBSYSTEM" <linux-gpio@vger.kernel.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Linus Walleij <linus.walleij@linaro.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH v9 07/20] gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL
Date: Sat, 26 Sep 2020 17:16:31 +0800 [thread overview]
Message-ID: <20200926091631.GA89482@sol> (raw)
In-Reply-To: <CAHp75VehvUTt19sBxgPTZszUmxDGZwqGAV7bgW5jVM8Mf63UJA@mail.gmail.com>
On Fri, Sep 25, 2020 at 01:06:02PM +0300, Andy Shevchenko wrote:
> On Thu, Sep 24, 2020 at 11:09 AM Kent Gibson <warthog618@gmail.com> wrote:
> > On Wed, Sep 23, 2020 at 02:11:54PM +0300, Andy Shevchenko wrote:
> > > On Tue, Sep 22, 2020 at 5:35 AM Kent Gibson <warthog618@gmail.com> wrote:
>
...
> > > > + /* Make sure this is terminated */
> > > > + ulr.consumer[sizeof(ulr.consumer)-1] = '\0';
> > > > + if (strlen(ulr.consumer)) {
> > > > + lr->label = kstrdup(ulr.consumer, GFP_KERNEL);
> > > > + if (!lr->label) {
> > > > + ret = -ENOMEM;
> > > > + goto out_free_linereq;
> > > > + }
> > > > + }
> > >
> > > Still don't get why we can\t use kstrndup() here...
> > >
> >
> > I know ;-).
> >
> > Another one directly from v1, and the behaviour there is to leave
> > lr->label nulled if consumer is empty.
> > It just avoids a pointless malloc for the null terminator.
>
> Again, similar as for bitmap API usage, if it makes code cleaner and
> increases readability, I will go for it.
> Also don't forget the army of janitors that won't understand the case
> and simply convert everything that can be converted.
>
Hmmm, there is more to it than I thought - gpiod_request_commit(),
which this code eventually calls, interprets a null label (not an
empty string) as indicating that the user has not set the label, in
which case it will set the desc label to "?". So userspace cannot
force the desc label to be empty.
We need to keep that label as null in that case to maintain that
behaviour.
I will add a comment there though.
Hmmm, having said that, does this form work for you:
if (ulr.consumer[0] != '\0') {
/* label is only initialized if consumer is set */
lr->label = kstrndup(ulr.consumer, sizeof(ulr.consumer) - 1, GFP_KERNEL);
...
It actually compiles slightly larger, I guess due to the extra parameter
in the kstrndup() call, but may be slightly more readable??
Cheers,
Kent.
next prev parent reply other threads:[~2020-09-26 9:16 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-22 2:31 [PATCH v9 00/20] gpio: cdev: add uAPI v2 Kent Gibson
2020-09-22 2:31 ` [PATCH v9 01/20] gpiolib: cdev: gpio_desc_to_lineinfo() should set info offset Kent Gibson
2020-09-22 2:31 ` [PATCH v9 02/20] gpiolib: cdev: replace strncpy() with strscpy() Kent Gibson
2020-09-22 2:31 ` [PATCH v9 03/20] gpio: uapi: define GPIO_MAX_NAME_SIZE for array sizes Kent Gibson
2020-09-22 2:31 ` [PATCH v9 04/20] gpio: uapi: define uAPI v2 Kent Gibson
2020-09-22 7:41 ` Arnd Bergmann
2020-09-22 9:50 ` Bartosz Golaszewski
2020-09-22 10:07 ` Kent Gibson
2020-09-23 10:04 ` Andy Shevchenko
2020-09-23 10:30 ` Kent Gibson
2020-09-23 11:16 ` Andy Shevchenko
2020-09-23 12:18 ` Arnd Bergmann
2020-09-23 15:15 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 05/20] gpiolib: make cdev a build option Kent Gibson
2020-09-22 2:31 ` [PATCH v9 06/20] gpiolib: add build option for CDEV v1 ABI Kent Gibson
2020-09-22 2:31 ` [PATCH v9 07/20] gpiolib: cdev: support GPIO_V2_GET_LINE_IOCTL and GPIO_V2_LINE_GET_VALUES_IOCTL Kent Gibson
2020-09-23 11:11 ` Andy Shevchenko
2020-09-24 8:09 ` Kent Gibson
2020-09-25 10:06 ` Andy Shevchenko
2020-09-26 9:16 ` Kent Gibson [this message]
2020-09-27 9:00 ` Andy Shevchenko
2020-09-27 12:39 ` Kent Gibson
2020-09-24 14:29 ` Bartosz Golaszewski
2020-09-22 2:31 ` [PATCH v9 08/20] gpiolib: cdev: support GPIO_V2_GET_LINEINFO_IOCTL and GPIO_V2_GET_LINEINFO_WATCH_IOCTL Kent Gibson
2020-09-23 15:41 ` Andy Shevchenko
2020-09-24 2:39 ` Kent Gibson
2020-09-24 8:39 ` Andy Shevchenko
2020-09-24 9:48 ` Kent Gibson
2020-09-25 10:12 ` Andy Shevchenko
2020-09-25 11:56 ` Kent Gibson
2020-09-25 14:43 ` Andy Shevchenko
2020-09-25 5:32 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 09/20] gpiolib: cdev: support edge detection for uAPI v2 Kent Gibson
2020-09-23 15:47 ` Andy Shevchenko
2020-09-24 3:07 ` Kent Gibson
2020-09-25 9:35 ` Andy Shevchenko
2020-09-25 12:26 ` Kent Gibson
2020-09-25 14:48 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 10/20] gpiolib: cdev: support GPIO_V2_LINE_SET_CONFIG_IOCTL Kent Gibson
2020-09-23 16:14 ` Andy Shevchenko
2020-09-23 16:15 ` Andy Shevchenko
2020-09-24 3:24 ` Kent Gibson
2020-09-24 8:26 ` Andy Shevchenko
2020-09-24 9:26 ` Kent Gibson
2020-09-25 9:49 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 11/20] gpiolib: cdev: support GPIO_V2_LINE_SET_VALUES_IOCTL Kent Gibson
2020-09-23 16:18 ` Andy Shevchenko
2020-09-24 7:32 ` Kent Gibson
2020-09-24 8:21 ` Andy Shevchenko
2020-09-24 9:08 ` Kent Gibson
2020-09-24 12:46 ` Kent Gibson
2020-09-25 9:57 ` Andy Shevchenko
2020-09-25 12:16 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 12/20] gpiolib: cdev: support setting debounce Kent Gibson
2020-09-23 16:27 ` Andy Shevchenko
2020-09-24 7:48 ` Kent Gibson
2020-09-25 9:43 ` Andy Shevchenko
2020-09-22 2:31 ` [PATCH v9 13/20] gpio: uapi: document uAPI v1 as deprecated Kent Gibson
2020-09-22 7:49 ` Arnd Bergmann
2020-09-22 8:11 ` Andy Shevchenko
2020-09-22 9:05 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 14/20] tools: gpio: port lsgpio to v2 uAPI Kent Gibson
2020-09-22 2:31 ` [PATCH v9 15/20] tools: gpio: port gpio-watch " Kent Gibson
2020-09-22 2:31 ` [PATCH v9 16/20] tools: gpio: rename nlines to num_lines Kent Gibson
2020-09-22 2:31 ` [PATCH v9 17/20] tools: gpio: port gpio-hammer to v2 uAPI Kent Gibson
2020-09-23 16:30 ` Andy Shevchenko
2020-09-24 7:50 ` Kent Gibson
2020-09-22 2:31 ` [PATCH v9 18/20] tools: gpio: port gpio-event-mon " Kent Gibson
2020-09-22 2:31 ` [PATCH v9 19/20] tools: gpio: add multi-line monitoring to gpio-event-mon Kent Gibson
2020-09-22 2:31 ` [PATCH v9 20/20] tools: gpio: add debounce support " Kent Gibson
2020-09-23 16:35 ` [PATCH v9 00/20] gpio: cdev: add uAPI v2 Andy Shevchenko
2020-09-24 8:00 ` Kent Gibson
2020-09-25 9:44 ` Andy Shevchenko
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