From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Henningsson Subject: Re: [PATCH 4/4 v4] ALSA: usb-audio: Scarlett mixer interface for 6i6, 18i6, 18i8 and 18i20 Date: Wed, 05 Nov 2014 10:55:38 +0100 Message-ID: <5459F41A.5060207@canonical.com> References: <1415055496-11151-1-git-send-email-chris.j.arges@canonical.com> <1415055496-11151-5-git-send-email-chris.j.arges@canonical.com> <54593304.8080701@canonical.com> <545934A3.4010600@canonical.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: Received: from youngberry.canonical.com (youngberry.canonical.com [91.189.89.112]) by alsa0.perex.cz (Postfix) with ESMTP id 23B51260695 for ; Wed, 5 Nov 2014 10:55:40 +0100 (CET) In-Reply-To: <545934A3.4010600@canonical.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: alsa-devel-bounces@alsa-project.org Sender: alsa-devel-bounces@alsa-project.org To: Chris J Arges , alsa-devel@alsa-project.org Cc: tiwai@suse.de, th55@gmx.de, robin@gareus.org, clemens@ladisch.de List-Id: alsa-devel@alsa-project.org On 2014-11-04 21:18, Chris J Arges wrote: > > > On 11/04/2014 02:11 PM, David Henningsson wrote: >> >> >> On 2014-11-03 23:58, Chris J Arges wrote: >>> This code contains the Scarlett mixer interface code that was originally >>> written by Tobias Hoffman and Robin Gareus. Because the device doesn't >>> properly implement UAC2 this code adds a mixer quirk for the device. >> >> Thanks a lot for taking over - it surely has been done with better speed >> than I would have. >> >>> + * Code cleanup: >>> + * David Henningsson >> >> Thanks for the credit, not sure I deserve it though, all I did was to >> squash the patches and fix the checkpatch errors :-) >> > : ) > >>> +static int scarlett_ctl_save_put(struct snd_kcontrol *kctl, >>> + struct snd_ctl_elem_value *ucontrol) >>> +{ >>> + struct usb_mixer_elem_info *elem = kctl->private_data; >>> + struct snd_usb_audio *chip = elem->mixer->chip; >>> + char buf[] = { 0x00, 0xa5 }; >>> + int err; >>> + >>> + if (ucontrol->value.enumerated.item[0] > 0) { >>> + err = snd_usb_ctl_msg(chip->dev, >>> + usb_sndctrlpipe(chip->dev, 0), UAC2_CS_MEM, >>> + USB_RECIP_INTERFACE | USB_TYPE_CLASS | >>> + USB_DIR_OUT, 0x005a, snd_usb_ctrl_intf(chip) | >>> + (0x3c << 8), buf, 2); >>> + if (err < 0) >>> + return err; >>> + >>> + usb_audio_info(elem->mixer->chip, >>> + "scarlett: saved settings to hardware.\n"); >>> + } >>> + return 0; >>> +} >> >> To elaborate on Takashi's concern about this control, imagine e g what >> alsactl restore/store being run on startup/shutdown. On shutdown, >> alsactl store would read "0", and on startup, alsactl restore would >> write "0", with the result that the hw would not store the values set. >> >> Would it be possible to have an autosave instead? E g, whenever a value >> is changed, it saves that value to the hardware. That's how other >> hardware works and what userspace expects. >> If you want to avoid a lot of autosaves, e g if the autosave takes a lot >> of time before the hw responds, maybe you could do the autosave in a 10 >> ms delayed_work, or similar. >> > > David, > Hey, as Tobias mentioned this is a HW saving (to the mixer's NVRAM) > function used for using the mixer disconnected from a computer. We > wouldn't want to continually write the NVRAM on every control update as > I'm unsure of how many write-cycles the device is capable of. > > So without it you can still plug the mixer into the computer and alsa > will restore any saved settings automatically. I'm planning on dropping > the HW Save in v5 until we can figure out a proper control mechanism for > this. Aha, sorry for not grasping that. Maybe "save to HW" could be labelled "save for offline use" or so. (Cool feature, btw. I didn't know that was possible.) I think a sysfs node would be simplest for this case. Just like we do "echo 1 > /sys/class/sound/hwC0D0/reconfig" to tell the HDA driver to reconfigure itself, there could be a "save_mixer_for_offline_use" node for this feature. -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic