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Re: [PATCH 01/11] audio: log unimplemented audio device sample rates
From: |
Christian Schoenebeck |
Subject: |
Re: [PATCH 01/11] audio: log unimplemented audio device sample rates |
Date: |
Sun, 18 Dec 2022 21:26:16 +0100 |
On Sunday, December 18, 2022 6:15:29 PM CET Volker Rümelin wrote:
> Some emulated audio devices allow guests to select very low
> sample rates that the audio subsystem doesn't support. The lowest
> supported sample rate depends on the audio backend used and in
> most cases can be changed with various -audiodev arguments. Until
> now, the audio_bug function emits an error message similar to the
> following error message
>
> A bug was just triggered in audio_calloc
> Save all your work and restart without audio
> I am sorry
> Context:
> audio_pcm_sw_alloc_resources_out passed invalid arguments to
> audio_calloc
> nmemb=0 size=16 (len=0)
> audio: Could not allocate buffer for `ac97.po' (0 samples)
>
> and the audio subsystem continues without sound for the affected
> device.
>
> The fact that the selected sample rate is not supported is not a
> guest error. Instead of displaying an error message, the missing
> audio support is now logged. Simply continuing without sound is
> correct, since the audio stream won't transport anything
> reasonable at such high resample ratios anyway.
>
> The AUD_open_* functions return NULL like before. The opened
> audio device will not be registered in the audio subsystem and
> consequently the audio frontend callback functions will not be
> called. The AUD_read and AUD_write functions return early in this
> case. This is necessary because, for example, the Sound Blaster 16
> emulation calls AUD_write from the DMA callback function.
>
> Signed-off-by: Volker Rümelin <vr_qemu@t-online.de>
> ---
> audio/audio.c | 1 +
> audio/audio_template.h | 13 +++++++++++++
> 2 files changed, 14 insertions(+)
>
> diff --git a/audio/audio.c b/audio/audio.c
> index d849a94a81..f6b420688d 100644
> --- a/audio/audio.c
> +++ b/audio/audio.c
> @@ -31,6 +31,7 @@
> #include "qapi/qobject-input-visitor.h"
> #include "qapi/qapi-visit-audio.h"
> #include "qemu/cutils.h"
> +#include "qemu/log.h"
> #include "qemu/module.h"
> #include "qemu/help_option.h"
> #include "sysemu/sysemu.h"
> diff --git a/audio/audio_template.h b/audio/audio_template.h
> index 720a32e57e..bfa94b4d22 100644
> --- a/audio/audio_template.h
> +++ b/audio/audio_template.h
> @@ -115,6 +115,19 @@ static int glue (audio_pcm_sw_alloc_resources_, TYPE)
> (SW *sw)
> #else
> samples = (int64_t)sw->HWBUF->size * sw->ratio >> 32;
> #endif
> + if (samples == 0) {
> + HW *hw = sw->hw;
> + size_t f_fe_min;
> +
> + /* f_fe_min = ceil(1 [frames] * f_be [Hz] / size_be [frames]) */
> + f_fe_min = (hw->info.freq + HWBUF->size - 1) / HWBUF->size;
> + qemu_log_mask(LOG_UNIMP,
> + AUDIO_CAP ": The guest selected a " NAME " sample rate"
> + " of %d Hz for %s. Only sample rates >= %zu Hz are"
> + " supported.\n",
> + sw->info.freq, sw->name, f_fe_min);
> + return -1;
You probably want to `sw->buf = NULL;` before returning here, or adjust the
condition for the error message below.
The other thing that puzzles me, in error case these template functions return
-1, which would then be feed to g_malloc*()?
> + }
>
> sw->buf = audio_calloc(__func__, samples, sizeof(struct st_sample));
> if (!sw->buf) {
>
[PATCH 02/11] audio: don't show unnecessary error messages, Volker Rümelin, 2022/12/18