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Date:   Mon, 23 Oct 2023 17:50:00 +0200
Message-ID: <87edhlwd7b.wl-tiwai@suse.de>
From:   Takashi Iwai <tiwai@suse.de>
To:     Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
Cc:     anton.yakovlev@opensynergy.com, mst@redhat.com, perex@perex.cz,
        tiwai@suse.com, virtualization@lists.linux-foundation.org,
        alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        pbonzini@redhat.com, stefanha@redhat.com, sgarzare@redhat.com,
        manos.pitsidianakis@linaro.org, mripard@redhat.com
Subject: Re: [PATCH v3] ALSA: virtio: use ack callback
In-Reply-To: <ZTaMEUZUTrRRUD6y@fedora>
References: <ZTaMEUZUTrRRUD6y@fedora>
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On Mon, 23 Oct 2023 17:06:57 +0200,
Matias Ezequiel Vara Larsen wrote:
> 
> +static int virtsnd_pcm_ack(struct snd_pcm_substream *substream)
> +{
> +	struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream);
> +	struct virtio_snd_queue *queue = virtsnd_pcm_queue(vss);
> +	unsigned long flags;
> +	struct snd_pcm_runtime *runtime = vss->substream->runtime;
> +	ssize_t appl_pos = frames_to_bytes(runtime, runtime->control->appl_ptr);
> +	ssize_t buf_size = frames_to_bytes(runtime, runtime->buffer_size);
> +	int rc;
> +
> +	spin_lock_irqsave(&queue->lock, flags);
> +	spin_lock(&vss->lock);
> +
> +	ssize_t bytes = (appl_pos - vss->appl_ptr) % buf_size;

The variable declaration should be moved to the beginning of the
function.

Also, there can be a overlap beyond runtime->boundary (which easily
happens for 32bit apps), so the calculation can be a bit more complex
with conditional.


thanks,

Takashi