Created attachment 40869 [details] PCM ioctls updates Hi Samuel Thibault <samuel.thibault@ens-lyon.org> provided in Debian bug http://bugs.debian.org/296323 a patch for the bug he describes as follows: """ Upon ioctl(fd, SNDCTL_DSP_GETBLKSIZE, &blockSize); valgrind complains if blockSize was not initialized. But its value is really not read by the kernel before being written to. And ioctl(fd, SNDCTL_DSP_SETFMT, &format); is not recognized as reading and then writing a value. """ Some time later, he provided an updated patch in Debian bug http://bugs.debian.org/305051 which I'll attach here. Thanks,
The patch isn't quite right, because GETBLKSIZE still needs to do a PRE_MEM_WRITE before the calls. Also SETFMT needs to do a POST_MEM_WRITE afterwards as the kernel will return a value. You also haven't said why you're removing the extra case for PCM_READ_BITS, which doesn't seem to be in the original patch on the debian bug.
Ughh.... I see now... That extra READ_BITS case is actually the same as SETFMT because it is forcing the W bit... Does that mean PCM_READ_BITS used to be declared as WR and then got fixed, and it's old ioctl got reused for SETFMT? That would be really nasty... To be honest overloading the same ioctl number for different things based on the R/W bits is just horrible anyway.
Improved patch committed as r11050.
I'm afraid I don't have the technical background on the patch, albeit I did point the submitter / original author at this bug; perhaps he will comment. Thanks a lot for improving/fixing and committing the patch!