From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.tuxedocomputers.com (mail.tuxedocomputers.com [157.90.84.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5517024B33; Tue, 19 Mar 2024 15:26:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=157.90.84.7 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710861995; cv=none; b=uIBV9Zvs3FHpikLBsTaqY6OWH9CbRKEOJz6f2kGQZ7nzKYRXba3/gUBZ4hHN20pG+Q/1EKaBqksgv3qqOwzGo20wYyStyRuD2ZTUD8yxPzyfrmVFPGZkfN8hfT2gpZKr9gMg2cmJDvJsas7IQfbvw96QZ3htNui/PN0sG7xdoUc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1710861995; c=relaxed/simple; bh=yNuXDV24kN5Tq58Ff6lS2FO83vxVjbX+X+J+Juwqd4Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=E6Fs4rAAGvVN6T+SJQQrEkwVylz4I7Idlp8XnyqYUH7GMNv4HhbycXjYi0jfOFFVq/9N6B0GNj+WihZt6ykLU8cwR4vwsi3vHpZHLXr9wTxgL2ThLF3zIvlZWzGm/hycL4g8iu26wwsYe0x7hmjg61y9ts3PCDUt9UQ4QOazDDA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=tuxedocomputers.com; spf=pass smtp.mailfrom=tuxedocomputers.com; dkim=pass (1024-bit key) header.d=tuxedocomputers.com header.i=@tuxedocomputers.com header.b=TmXklku9; arc=none smtp.client-ip=157.90.84.7 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=tuxedocomputers.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tuxedocomputers.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=tuxedocomputers.com header.i=@tuxedocomputers.com header.b="TmXklku9" Received: from [192.168.42.20] (pd9e59c8a.dip0.t-ipconnect.de [217.229.156.138]) (Authenticated sender: wse@tuxedocomputers.com) by mail.tuxedocomputers.com (Postfix) with ESMTPSA id 873592FC010D; Tue, 19 Mar 2024 16:18:41 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tuxedocomputers.com; s=default; t=1710861522; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=OLYrKqHUM/IS0ZPTvZGbAWfjnkzw3USLCJuf00OnxW8=; b=TmXklku9GoSmsAqKgvFjAdvKArNOxe6Ng926gjBEtTf3XVHFd/jpvZ05aFiBmld1CLguCq muxHUNdiSvwyaj1HS4SM2wSgyiAPBU5Dxil0wx0FqvM6OC6irM8F8Sz1HUvSQibYPNc+iL 4yi62HVK0MqzxvgZENWETG1QP4z7yRg= Authentication-Results: mail.tuxedocomputers.com; auth=pass smtp.auth=wse@tuxedocomputers.com smtp.mailfrom=wse@tuxedocomputers.com Message-ID: <93d70ac3-bb18-4732-abb4-134750a5b50c@tuxedocomputers.com> Date: Tue, 19 Mar 2024 16:18:40 +0100 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Future handling of complex RGB devices on Linux v3 To: Hans de Goede Cc: Lee Jones , jikos@kernel.org, linux-kernel@vger.kernel.org, Jelle van der Waa , Miguel Ojeda , "dri-devel@lists.freedesktop.org" , linux-input@vger.kernel.org, ojeda@kernel.org, linux-leds@vger.kernel.org, Pavel Machek , Gregor Riepl References: <0cdb78b1-7763-4bb6-9582-d70577781e61@tuxedocomputers.com> <7228f2c6-fbdd-4e19-b703-103b8535d77d@redhat.com> <730bead8-6e1d-4d21-90d2-4ee73155887a@tuxedocomputers.com> <952409e1-2f0e-4d7a-a7a9-3b78f2eafec7@redhat.com> <9851a06d-956e-4b57-be63-e10ff1fce8b4@tuxedocomputers.com> <1bc6d6f0-a13d-4148-80cb-9c13dec7ed32@redhat.com> <477d30ee-247e-47e6-bc74-515fd87fdc13@redhat.com> <247b5dcd-fda8-45a7-9896-eabc46568281@tuxedocomputers.com> <825129ea-d389-4c6c-8a23-39f05572e4b4@redhat.com> <281f9b71-a565-4ff3-8343-ca36d604584d@redhat.com> Content-Language: en-US From: Werner Sembach In-Reply-To: <281f9b71-a565-4ff3-8343-ca36d604584d@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Hans, Am 18.03.24 um 12:11 schrieb Hans de Goede: > Hi Werner, > > Sorry for the late reply. np > > On 2/22/24 2:14 PM, Werner Sembach wrote: >> Hi, >> >> Thanks everyone for the exhaustive feedback. And at least this thread is a good comprehesive reference for the future ^^. >> >> To recap the hopefully final UAPI for complex RGB lighting devices: >> >> - By default there is a singular /sys/class/leds/* entry that treats the device as if it was a single zone RGB keyboard backlight with no special effects. > Ack this sounds good. > >> - There is an accompanying misc device with the sysfs attributes "name", "device_type",  "firmware_version_string", "serial_number" for device identification and "use_leds_uapi" that defaults to 1. > You don't need a char misc device here, you can just make this sysfs attributes on the LED class device's parent device by using device_driver.dev_groups. Please don't use a char misc device just to attach sysfs attributes to it. > > Also I'm a bit unsure about most of these attributes, "use_leds_uapi" was discussed before > and makes sense. But at least for HID devices the rest of this info is already available > in sysfs attributes on the HID devices (things like vendor and product id) and since the > userspace code needs per device code to drive the kbd anyways it can also have device > specific code to retrieve all this info, so the other sysfs attributes just feel like > duplicating information. Also there already are a ton of existing hidraw userspace rgbkbd > drivers which already get this info from other places. The parent device can be a hid device, a wmi device, a platform device etc. so I thought it would be nice to have some unified way for identification. > >>     - If set to 0 the /sys/class/leds/* entry disappears. The driver should keep the last state the backlight was in active if possible. >> >>     - If set 1 it appears again. The driver should bring it back to a static 1 zone setting while avoiding flicker if possible. > Ack, if this finds it way into some documentation (which it should) please make it > clear that this is about the "use_leds_uapi" sysfs attribute. Ack > >> - If the device is not controllable by for example hidraw, the misc device might also implement additional ioctls or sysfs attributes to allow a more complex low level control for the keyboard backlight. This is will be a highly vendor specific UAPI. > IMHO this is the only case where actually using a misc device makes sense, so that > you have a chardev to do the ioctls on. misc-device-s should really only be used > when you need a chardev under /dev . Since you don't need the chardev for the e.g. > hidraw case you should not use a miscdev there IMHO. My train of thought was that it would be nice to have the use_leds_uapi at a somewhat unified location in sysfs. The parent device can be of any kind, like I mentioned above, and while for deactivating it can easily be found via /sys/class/leds/*/device/. For reactivating, the leds entry doesn't exist. > >>     - The actual logic interacting with this low level UAPI is implemented by a userspace driver >> >> Implementation wise: For the creation of the misc device with the use_leds_uapi switch a helper function/macro might be useful? Wonder if it should go into leds.h, led-class-multicolor.h, or a new header file? > See above, I don't think we want the misc device for the hidraw case, at which > point I think the helper becomes unnecessary since just a single sysfs write > callback is necessary. > > Also for adding new sysfs attributes it is strongly encouraged to use > device_driver.dev_groups so that the device core handled registering / > unregistering the sysfs attributes which fixes a bunch of races; and > using device_driver.dev_groups does not mix well with a helper as you've > suggested. Ok, I will see when I start implementing. > >> - Out of my head it would look something like this: >> >> led_classdev_add_optional_misc_control( >>     struct led_classdev *led_cdev, >>     char* name, >>     char* device_type, >>     char* firmware_version_string, >>     char* serial_number, >>     void (*deregister_led)(struct led_classdev *led_cdev), >>     void (*reregister_led)(struct led_classdev *led_cdev)) >> >> Let me know your thoughts and hopefully I can start implementing it soon for one of our devices. > I think overall the plan sounds good, with my main suggested change > being to not use an unnecessary misc device for the hid-raw case. > > Regards, > > Hans > > Thanks for the feedback, Werner