Re: [PATCH 5/5] firmware: add DECLARE_FW_CUSTOM_FALLBACK() annotation

Jacek Anaszewski
2016-12-15T09:33:05Z

Hi Luis,

Thanks for the patch.

On 12/13/2016 04:08 AM, Luis R. Rodriguez wrote:
> We need to ensure that when driver developers use the custom firmware
> fallback mechanism it was not a copy and paste bug. These use cases on
> upstream drivers are rare, we only have 2 upstream users and its for
> really old drivers. Since valid uses are rare but possible enable a
> white-list for its use, and use this same white-list annotation to refer
> to the documentation covering the custom use case.
>
> New faulty users can be reported via 0-day now.
>
> Cc: Fengguang Wu <fengguang.wu@intel.com>
> Cc: Richard Purdie <rpurdie@rpsys.net>
> Cc: Jacek Anaszewski <j.anaszewski@samsung.com>
> Cc: linux-leds@vger.kernel.org
> Cc: Abhay Salunke <Abhay_Salunke@dell.com>
> Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
> ---
> Documentation/driver-api/firmware/fallback-mechanisms.rst | 7 +++++--
> drivers/firmware/dell_rbu.c | 1 +
> drivers/leds/leds-lp55xx-common.c | 1 +
> include/linux/firmware.h | 7 +++++++
> scripts/coccinelle/api/request_firmware-custom-fallback.cocci | 9 ++++++++-
> 5 files changed, 22 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/driver-api/firmware/fallback-mechanisms.rst b/Documentation/driver-api/firmware/fallback-mechanisms.rst
> index 955c11d6ff9d..b51673e40439 100644
> --- a/Documentation/driver-api/firmware/fallback-mechanisms.rst
> +++ b/Documentation/driver-api/firmware/fallback-mechanisms.rst
> @@ -184,8 +184,11 @@ load firmware for you through a custom path.
>
> The custom fallback mechanism can often be enabled by mistake. We currently
> have only 2 users of it, and little justification to enable it for other users.
> -Since it is a common driver developer mistake to enable it, help police for
> -new users of the custom fallback mechanism with::
> +Since it is a common driver developer mistake to enable it, driver developers
> +should use DECLARE_FW_CUSTOM_FALLBACK() to both white-list and validate their
> +use and also refer to the documentation for the custom loading solution.
> +
> +Invalid users of the custom fallback mechanism can be policed using::

double colon at the end of line

>
> $ export COCCI=scripts/coccinelle/api/request_firmware-avoid-init-probe-init.cocci
> $ make coccicheck MODE=report
> diff --git a/drivers/firmware/dell_rbu.c b/drivers/firmware/dell_rbu.c
> index 2f452f1f7c8a..3f2aa35bc54d 100644
> --- a/drivers/firmware/dell_rbu.c
> +++ b/drivers/firmware/dell_rbu.c
> @@ -586,6 +586,7 @@ static ssize_t read_rbu_image_type(struct file *filp, struct kobject *kobj,
> return size;
> }
>
> +DECLARE_FW_CUSTOM_FALLBACK("Documentation/dell_rbu.txt");
> static ssize_t write_rbu_image_type(struct file *filp, struct kobject *kobj,
> struct bin_attribute *bin_attr,
> char *buffer, loff_t pos, size_t count)
> diff --git a/drivers/leds/leds-lp55xx-common.c b/drivers/leds/leds-lp55xx-common.c
> index 5377f22ff994..04161428ee3b 100644
> --- a/drivers/leds/leds-lp55xx-common.c
> +++ b/drivers/leds/leds-lp55xx-common.c
> @@ -219,6 +219,7 @@ static void lp55xx_firmware_loaded(const struct firmware *fw, void *context)
> release_firmware(chip->fw);
> }
>
> +DECLARE_FW_CUSTOM_FALLBACK("Documentation/leds/leds-lp55xx.txt");
> static int lp55xx_request_firmware(struct lp55xx_chip *chip)
> {

For this LED class driver:

Acked-by: Jacek Anaszewski <j.anaszewski@samsung.com>

> const char *name = chip->cl->name;
> diff --git a/include/linux/firmware.h b/include/linux/firmware.h
> index b1f9f0ccb8ac..e6ca19c03dcc 100644
> --- a/include/linux/firmware.h
> +++ b/include/linux/firmware.h
> @@ -8,6 +8,13 @@
> #define FW_ACTION_NOHOTPLUG 0
> #define FW_ACTION_HOTPLUG 1
>
> +/*
> + * Helper for scripts/coccinelle/api/request_firmware-custom-fallback.cocci
> + * and so users can also easily search for the documentation for the
> + * respectively needed custom fallback mechanism.
> + */
> +#define DECLARE_FW_CUSTOM_FALLBACK(__usermode_helper)
> +
> struct firmware {
> size_t size;
> const u8 *data;
> diff --git a/scripts/coccinelle/api/request_firmware-custom-fallback.cocci b/scripts/coccinelle/api/request_firmware-custom-fallback.cocci
> index c7598cfc4780..68cacab35b76 100644
> --- a/scripts/coccinelle/api/request_firmware-custom-fallback.cocci
> +++ b/scripts/coccinelle/api/request_firmware-custom-fallback.cocci
> @@ -17,6 +17,13 @@
> virtual report
> virtual context
>
> +@ r0 depends on report || context @
> +declarer name DECLARE_FW_CUSTOM_FALLBACK;
> +expression E;
> +@@
> +
> +DECLARE_FW_CUSTOM_FALLBACK(E);
> +
> @ r1 depends on report || context @
> expression mod, name, dev, gfp, drv, cb;
> position p;
> @@ -30,7 +37,7 @@ position p;
> *request_firmware_nowait@p(mod, FW_ACTION_NOHOTPLUG, name, dev, gfp, drv, cb)
> )
>
> -@script:python depends on report@
> +@script:python depends on report && !r0 @
> p << r1.p;
> @@
>
>

--
Best regards,
Jacek Anaszewski