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hw/audio/lm4549: Don't try to open a zero-frequency audio voice

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If the guest incorrectly programs the lm4549 audio chip with a zero
frequency, we will pass this to AUD_open_out(), which will complain:

   A bug was just triggered in AUD_open_out
   Save all your work and restart without audio
   I am sorry
   Context:
   audio: frequency=0 nchannels=2 fmt=S16 endianness=little

The datasheet doesn't say what we should do here, only that the valid
range for the freqency is 4000 to 48000 Hz; we choose to log the
guest error and ignore an attempt to change the DAC rate to something
outside the valid range.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/410
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-id: 20251107154116.1396769-1-peter.maydell@linaro.org
This commit is contained in:
Peter Maydell 2025-11-07 15:41:16 +00:00
parent 5fc50b4ec8
commit 522444744e
1 changed files with 16 additions and 1 deletions
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17
hw/audio/lm4549.c
View file

@ -15,6 +15,7 @@
#include "qemu/osdep.h"
#include "hw/hw.h"
#include "qemu/log.h"
#include "qemu/audio.h"
#include "lm4549.h"
#include "migration/vmstate.h"
@ -179,9 +180,23 @@ void lm4549_write(lm4549_state *s,
break;
case LM4549_PCM_Front_DAC_Rate:
regfile[LM4549_PCM_Front_DAC_Rate] = value;
DPRINTF("DAC rate change = %i\n", value);
/*
* Valid sample rates are 4kHz to 48kHz.
* The datasheet doesn't say what happens if you try to
* set the frequency to zero. AUD_open_out() will print
* a bug message if we pass it a zero frequency, so just
* ignore attempts to set the DAC frequency to zero.
*/
if (value < 4000 || value > 48000) {
qemu_log_mask(LOG_GUEST_ERROR,
"%s: DAC sample rate %d Hz is invalid, ignoring it\n",
__func__, value);
break;
}
regfile[LM4549_PCM_Front_DAC_Rate] = value;
/* Re-open a voice with the new sample rate */
struct audsettings as;
as.freq = value;