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[2001:1c00:c14:2800:ec23:a060:24d5:2453]) by smtp.gmail.com with ESMTPSA id ba28sm1752166edb.4.2019.10.05.02.53.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 05 Oct 2019 02:53:35 -0700 (PDT) Subject: Re: [PATCH v7 4/8] firmware: Add new platform fallback mechanism and firmware_request_platform() To: Dmitry Torokhov Cc: Ard Biesheuvel , Darren Hart , Andy Shevchenko , Luis Chamberlain , Greg Kroah-Hartman , "Rafael J . Wysocki" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H . Peter Anvin" , Jonathan Corbet , Peter Jones , Dave Olsthoorn , x86@kernel.org, platform-driver-x86@vger.kernel.org, linux-efi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-input@vger.kernel.org References: <20191004145056.43267-1-hdegoede@redhat.com> <20191004145056.43267-5-hdegoede@redhat.com> <20191004231733.GF22365@dtor-ws> From: Hans de Goede Message-ID: Date: Sat, 5 Oct 2019 11:53:34 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <20191004231733.GF22365@dtor-ws> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org 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