Re: [alsa-devel] [PATCH] hda - fail ELD reading early

At Tue, 22 Nov 2011 16:46:23 +0800, Wu Fengguang wrote:

With the ELD repoll mechanism, we can (and should) fail the ELD reading immediately when find something obviously wrong and let the caller retry after some delay.

Signed-off-by: Wu Fengguang fengguang.wu@intel.com

sound/pci/hda/hda_eld.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-)

--- linux.orig/sound/pci/hda/hda_eld.c 2011-11-22 16:02:58.000000000 +0800 +++ linux/sound/pci/hda/hda_eld.c 2011-11-22 16:36:10.000000000 +0800 @@ -347,18 +347,28 @@ int snd_hdmi_get_eld(struct hdmi_eld *el

for (i = 0; i < size; i++) { unsigned int val = hdmi_get_eld_data(codec, nid, i);

• /*
  

•  * Graphics driver might be writing to ELD buffer right now.
  

•  * Just abort. The caller will repoll after a while.
  

•  */
  

  if (!(val & AC_ELDD_ELD_VALID)) {

• 	if (!i) {
  

• 		snd_printd(KERN_INFO
  

• 			   "HDMI: invalid ELD data\n");
  

• 		ret = -EINVAL;
  

• 		goto error;
  

• 	}
  snd_printd(KERN_INFO
  	  "HDMI: invalid ELD data byte %d\n", i);
  

• 	val = 0;
  

• } else
  

• 	val &= AC_ELDD_ELD_DATA;
  

• 	ret = -EINVAL;
  

• 	goto error;
  

• }
  

• val &= AC_ELDD_ELD_DATA;
  

• /*
  

•  * The first byte cannot be zero. This can happen on some DVI
  

•  * connections. Some Intel chips may also need some 250ms delay
  

•  * to return non-zero ELD data, even when the graphics driver
  

•  * correctly writes ELD content before setting ELD_valid bit.
  

•  */
  

• if (!val && !i) {
  

• 	snd_printdd(KERN_INFO "HDMI: 0 ELD data\n");
  

• 	ret = -EINVAL;
  

• 	goto error;
  

• }
  

Shouldn't this zero-check be before the valid-bit check? Otherwise it'll never reach there.

thanks,

Takashi