linux-kernel - Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]

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Message-ID: <47663431.8000603@msgid.tls.msk.ru>
Date:	Mon, 17 Dec 2007 11:32:49 +0300
From:	Michael Tokarev <mjt@....msk.ru>
To:	Kay Sievers <kay.sievers@...y.org>
CC:	linux-kernel@...r.kernel.org, Greg KH <greg@...ah.com>
Subject: Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block	device
 in sysfs]

Kay Sievers wrote:
> On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote:
[]
>> How to distinguish char devices from block devices in sysfs?
>> Is the only way to read a symlink `subsystem' in the device
>> directory?
> 
> By its subsystem value (block), from the symlink, from the environment,
> or from $1.

Environment and $1 comes as arguments for hotplug helper, not
when scanning /sys/.

>> For now, I've a shell code (used heavily in numerous places),
>> which looks like this:
>>
>>   function makedev() {
>>     ...
>>     case $DEVPATH in
>>       /block/*) TYPE=b ;;
>>       *) TYPE=c ;;
>>     esac
>>     ...
>>     mknod /dev/$DEV $TYPE $MAJOR $MINOR
>>   }
>>
>> The only external process invocation in there is mknod, all
>> the rest is done using pure shell constructs.  Is it really
>> necessary to spawn another process just to read a symlink
>> now?  It will be almost 2 times slower....
> 
> No need.

It seems there IS a need now ;)

Thanks for the clarification.

/mjt
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