Problem with buffer/period sizes.

[James Courtier-Dutton <James@superbug.demon.co.uk>]

I have code that looks like the following: -

err = snd_pcm_hw_params_get_buffer_size_min(params, &buffer_size_min);
err = snd_pcm_hw_params_get_buffer_size_max(params, &buffer_size_max);
dir=0;
err = snd_pcm_hw_params_get_period_size_min(params, &period_size_min,&dir);
dir=0;
err = snd_pcm_hw_params_get_period_size_max(params, &period_size_max,&dir);

<snip> some calculations happen here

err = snd_pcm_hw_params_set_buffer_size_near(audio_fd, params, 
&buffer_size);
dir=0;
err = snd_pcm_hw_params_set_period_size_near(audio_fd, params, 
&period_size, &dir);

For a snd_intel8x0 driver with INTEL ICH5 chip with
PCI IDs of 0x8086, 0x24d5
Displays: -
buffer_size_min/max = 64 / 16384
period_size_min/max = 16 / 16384

We then try to set: -
buffer_size = 16384
period_size =  2048
And it accepts those settings, and works.

For a snd_intel8x0 driver with NVIDIA NFORCE chip with
PCI IDs of 0x10de, 0x01b1
Displays: -
buffer_size_min/max = 67 / 15052
period_size_min/max =  7 / 15053

We then try to set: -
buffer_size = 15048
period_size =  1881
But, this sets a period size = buffer_size = 15048 which then fails to 
work due to not having 2 periods or more.

What is causing the NFORCE chip to suggest such strange values, and then 
to not accept those values.

Cheers
James



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