linux-kernel - Re: [PATCH v4 01/11] ASoC: SOF: core: add 'no

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Date:   Fri, 1 Sep 2023 15:22:50 +0300 (EEST)
From:   Kai Vehmanen <kai.vehmanen@...ux.intel.com>
To:     Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
cc:     Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        alsa-devel@...a-project.org, Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Baluta <daniel.baluta@....com>,
        linux-kernel@...r.kernel.org, sound-open-firmware@...a-project.org
Subject: Re: [PATCH v4 01/11] ASoC: SOF: core: add 'no_wq' probe and remove
 callbacks

Hi,

On Wed, 30 Aug 2023, Pierre-Louis Bossart wrote:

> >  	/* probe/remove/shutdown */
> > +	int (*probe_no_wq)(struct snd_sof_dev *sof_dev); /* optional */
> > +	int (*remove_no_wq)(struct snd_sof_dev *sof_dev); /* optional */
> 
> My initial PR didn't have this remove_no_wq() callback.
> 
> For symmetry it could be useful if it is meant to undo what the
> probe_no_wq() did, but conceptually the first thing we do in the remove
> is make sure that workqueue is either not scheduled or we wait until it
> completes.

I think that's exactly what the patch ends up with, remove_no_wq releases 
resources acquired in probe_no_wq, i.e. they are symmetrical.
 
> int snd_sof_device_remove(struct device *dev)
> {
> 	struct snd_sof_dev *sdev = dev_get_drvdata(dev);
> 	struct snd_sof_pdata *pdata = sdev->pdata;
> 	int ret;
> 
> 	if (IS_ENABLED(CONFIG_SND_SOC_SOF_PROBE_WORK_QUEUE))
> 		cancel_work_sync(&sdev->probe_work);

So this seems ok as well:
 - if wq is used, at remove, we first wait wq to be finished 
   and only then proceed with removal
 - the remove_no_wq is run only when the first step is completed

Br, Kai