Re: [PATCH v7 4/8] firmware: Add new platform fallback mechanism and firmware_request_platform()

Dmitry Torokhov
2019-10-04T23:17:38Z

Hi Hans,

On Fri, Oct 04, 2019 at 04:50:52PM +0200, Hans de Goede wrote:
> In some cases the platform's main firmware (e.g. the UEFI fw) may contain
> an embedded copy of device firmware which needs to be (re)loaded into the
> peripheral. Normally such firmware would be part of linux-firmware, but in
> some cases this is not feasible, for 2 reasons:
>
> 1) The firmware is customized for a specific use-case of the chipset / use
> with a specific hardware model, so we cannot have a single firmware file
> for the chipset. E.g. touchscreen controller firmwares are compiled
> specifically for the hardware model they are used with, as they are
> calibrated for a specific model digitizer.
>
> 2) Despite repeated attempts we have failed to get permission to
> redistribute the firmware. This is especially a problem with customized
> firmwares, these get created by the chip vendor for a specific ODM and the
> copyright may partially belong with the ODM, so the chip vendor cannot
> give a blanket permission to distribute these.
>
> This commit adds a new platform fallback mechanism to the firmware loader
> which will try to lookup a device fw copy embedded in the platform's main
> firmware if direct filesystem lookup fails.
>
> Drivers which need such embedded fw copies can enable this fallback
> mechanism by using the new firmware_request_platform() function.

Why would drivers not want to fetch firmware from system firmware if it
is not present on disk? I would say let driver to opt-out of this
fallback, but default request_firmware() should do it by default.

Thanks.

--
Dmitry