Calculus: Added category

2011-10-28T06:51:33Z

Added category

GNUtoo at 21:08, 28 June 2010

2010-06-28T21:08:10Z

GNUtoo: Created page with '== Introduction == Sometimes some applications block, and strace show something like that: ioctl(6, 0x400c4150 which means that the kernel blocks during that ioctl. =…'

2010-06-28T21:07:19Z

Created page with '== Introduction == Sometimes some applications block, and strace show something like that: ioctl(6, 0x400c4150 which means that the kernel blocks during that ioctl. =…'

New page

== Introduction ==
Sometimes some applications block, and [[Strace|strace]] show something like that:
ioctl(6, 0x400c4150
which means that the kernel blocks during that ioctl.
== Howto ==
we will take the same example than before,with mplayer blocking.:
ioctl(6, 0x400c4150
there are two important information in it:
6 is the file descriptor,the corresponding file can be found with:
ls -l /proc/$(pidof mplayer)/fd/6
which gives
/dev/snd/pcmC0D0p
That correspond to alsa.
Then we have the 0x400c4150
the important part is the last part:
41 is 0x41 which is often represented as a letter and can be decoded like this:
$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import binascii
>>> binascii.a2b_hex("41")
'A'
Or verified like this:
$ python
Python 2.6.5 (r265:79063, Apr 16 2010, 13:57:41)
[GCC 4.4.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import binascii
>>> binascii.b2a_hex("A")
'41'

Then 0x50 remains. we don't need to decode it,it's fine like it is.

so with A and 50 and /dev/snd/pcmC0D0p file we can go to grep in include/sound of the kernel sources:
include/sound$ grep "0x50" *
ac97_codec.h:#define AC97_GPIO_STICKY 0x50 /* GPIO Pin Sticky, 0=not, 1=sticky */
ad1816a.h:#define AD1816A_SRC_MIC 0x50
ad1816a.h:#define AD1816A_SRC_MONO 0x50
asequencer.h:#define SNDRV_SEQ_IOCTL_GET_SUBSCRIPTION _IOWR('S', 0x50, struct snd_seq_port_subscribe)
asoundef.h:#define MIDI_CTL_GENERAL_PURPOSE5 0x50
asound.h:#define SNDRV_PCM_IOCTL_WRITEI_FRAMES _IOW('A', 0x50, struct snd_xferi)
cs46xx.h:#define HDCR_SMS_256_DWORDS 0x50000000
cs46xx.h:#define DMA_RQ_C1_SOURCE_MOD256 0x50000000
emu10k1.h:#define CDCS 0x50 /* CD-ROM digital channel status register */
emu10k1.h:#define C_ffffffff 0x50
emu10k1.h:#define A_P16VIN(x) (0x50 + (x)) /* x = 0x00 - 0x0f p16v ins (A2 only) "EMU32 inputs" */
gus.h:#define SNDRV_GF1_GB_DRAM_DMA_HIGH 0x50
sb.h:#define SB_ALS4000_3D_SND_FX 0x50
trident.h:#define SI_ASR0 0x50
here we see:
asound.h:#define SNDRV_PCM_IOCTL_WRITEI_FRAMES _IOW('A', 0x50, struct snd_xferi)
which is our ioctl.

The next step is to look where this ioctl is called:

← Older revision		Revision as of 06:51, 28 October 2011
Line 60:		Line 60:

	Then good luck for debugging your driver...		Then good luck for debugging your driver...
		+
		+	[[Category:Embedded Dictionary]]

← Older revision		Revision as of 21:08, 28 June 2010
Line 54:		Line 54:

	The next step is to look where this ioctl is called:		The next step is to look where this ioctl is called:
		+	sound$ grep SNDRV_PCM_IOCTL_WRITEI_FRAMES -r *
		+	core/pcm_native.c: case SNDRV_PCM_IOCTL_WRITEI_FRAMES:
		+	core/pcm_compat.c: SNDRV_PCM_IOCTL_WRITEI_FRAMES32 = _IOW('A', 0x50, struct snd_xferi32),
		+	core/pcm_compat.c: case SNDRV_PCM_IOCTL_WRITEI_FRAMES32:
		+
		+	Then good luck for debugging your driver...

Ioctl - Revision history

Calculus: Added category

GNUtoo at 21:08, 28 June 2010

GNUtoo: Created page with '== Introduction == Sometimes some applications block, and strace show something like that: ioctl(6, 0x400c4150 which means that the kernel blocks during that ioctl. =…'