Re: [PATCH 8/8] ASoC: SOF: Intel: add .ack support for HDaudio platforms

From: Takashi Iwai <tiwai@suse.de>
To: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: alsa-devel@alsa-project.org, broonie@kernel.org,
	Ranjani Sridharan <ranjani.sridharan@linux.intel.com>,
	Kai Vehmanen <kai.vehmanen@linux.intel.com>
Subject: Re: [PATCH 8/8] ASoC: SOF: Intel: add .ack support for HDaudio platforms
Date: Sun, 13 Jun 2021 09:29:50 +0200	[thread overview]
Message-ID: <s5h35tm5ij5.wl-tiwai@suse.de> (raw)
In-Reply-To: <20210610205326.1176400-9-pierre-louis.bossart@linux.intel.com>

On Thu, 10 Jun 2021 22:53:26 +0200,
Pierre-Louis Bossart wrote:
> 
> +/* update SPIB register with appl position */
> +int hda_dsp_pcm_ack(struct snd_sof_dev *sdev, struct snd_pcm_substream *substream)
> +{
> +	struct hdac_stream *hstream = substream->runtime->private_data;
> +	struct hdac_ext_stream *stream = stream_to_hdac_ext_stream(hstream);
> +	struct snd_pcm_runtime *runtime = substream->runtime;
> +	ssize_t appl_pos, buf_size;
> +	u32 spib;
> +
> +	if (!hda_disable_rewinds)
> +		return 0;
> +
> +	/*
> +	 * paranoia check: if a rewind request took place after the RUN bits were programmed,
> +	 * deny it since hardware only supports monotonic (modulo) increments for SPIB.
> +	 */
> +	if (hstream->running) {
> +		if (runtime->control->appl_ptr < stream->old_appl_ptr)
> +			return -EINVAL;

This condition won't be enough when the appl_ptr overlap the buffer
boundary.  It's still possible on 32bit architecture.

thanks,

Takashi