Re: Missing MODALIAS in /sys/devices/system/cpu/uevent

[Pali RohÃr]

On Thursday 27 November 2014 21:39:42 Rafael J. Wysocki wrote:
> On Thursday, November 27, 2014 09:01:11 PM Pali RohÃr wrote:
> > --nextPart2712852.Yg3XtZvm05
> > Content-Type: Text/Plain;
> > 
> >   charset="utf-8"
> > 
> > Content-Transfer-Encoding: quoted-printable
> > 
> > Hello,
> > 
> > on 3.18-rc5 I have empty cpu uevent file, but modalias file
> > is=20 populated. See:
> > 
> > $ cat /sys/devices/system/cpu/uevent=20
> > $ cat /sys/devices/system/cpu/modalias=20
> > cpu:type:x86,ven0000fam0006mod003C:feature:,0000,0001,0002,0
> > 003,0004,0005,0=
> > 006,0007,0008,0009,000B,000C,000D,000E,000F,0010,0011,0013,
> > 0015,0016,0017,0=
> > 018,0019,001A,001B,001C,001D,001F,002B,0034,003A,003B,003D,
> > 0068,006B,006C,0=
> > 06D,006F,0070,0072,0074,0075,0076,0078,007C,007D,0080,0081,
> > 0082,0083,0084,0=
> > 085,0086,0087,0088,0089,008B,008C,008D,008E,008F,0091,0093,
> > 0094,0095,0096,0=
> > 097,0098,0099,009A,009B,009C,009D,009E,00C0,00C5,00E0,00E1,
> > 00E3,00E5,00E6,0=
> > 0E7,0100,0101,0102,0103,0104,0120,0121,0123,0124,0125,0127,
> > 0128,0129,012A,0= 12B,012D,0140
> > 
> > =46or all other devices in /sys/devices/ which have
> > modalias=20 content there is also MODALIAS=3D line in
> > uevent file.
> 
> /sys/devices/system/cpu/ is not a device.  It is a "collection
> of all CPUs".
> 

Ok. But why that inconsistency (missing MODALIAS line)?

> > Is cpu device special? Or why it is only one device which
> > has=20 modalias file but is missing MODALIAS=3D line in
> > uevent file?
> 
> Look into the uevent files under /sys/devices/system/cpu/cpu0/
> etc.
> 

$ cat /sys/devices/system/cpu/cpu0/modalias
cat: /sys/devices/system/cpu/cpu0/modalias: No such file or 
directory
$ cat /sys/devices/system/cpu/cpu0/uevent 
DRIVER=processor
MODALIAS=cpu:type:x86,ven0000fam0006mod003C:feature:,0000,0001,0002,0003,0004,0005,0006,0007,0008,0009,000B,000C,000D,000E,000F,0010,0011,0013,0015,0016,0017,0018,0019,001A,001B,001C,001D,001F,002B,0034,003A,003B,003D,0068,006B,006C,006D,006F,0070,0072,0074,0075,0076,0078,007C,007D,0080,0081,0082,0083,0084,0085,0086,0087,0088,0089,008B,008C,008D,008E,008F,0091,0093,0094,0095,0096,0097,0098,0099,009A,009B,009C,009D,009E,00C0,00C5,00E0,00E1,00E3,00E5,00E6,00E7,0100,0101,0102,0103,0104,0120,0121,0123,0124,0125,0127,0128,0129,012A,012B,012D,0140

So there is no modalias file, but uevent contains MODALIAS line.

> > What userspace application should use for reading
> > modalias=20 string? File modalias or file uevent?
> 
> The cpu modalias is used to trigger loading of some
> CPU-specific modules upfront IIRC.  So yes, it is special.
> 
> My advice would be to follow udev here.

Yes, I know. For some reasons coretemp.ko is not automatically 
loaded. I do not know why and I started investigating it. And I 
found above inconsistency in modalias and uevent...

$ modinfo coretemp
...
alias:          cpu:type:x86,ven0000fam*mod*:feature:*00E7*

-- 
Pali RohÃr
pali.rohar@xxxxxxxxx

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