Hi Dmitry,
On 05-10-2019 01:17, Dmitry Torokhov wrote:
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.
Only few devices / device-drivers have / need firmware which is
embedded in the system-fw. Checking for this introduces an extra call
in the firmware-loader path and the firmware-loader maintainer have
requested to make this opt-in, rather then opt-out, so that these changes
do not impact the many many other drivers which do not need this.
To be precise so far only the 2 touchscreen drivers for which patches
are in this series are known to benefit from this approach. So since this
is somewhat of a special case opt-in makes more sense then opt-out.
Regards,
Hans
