Excess spaces in sysfs files

Excess spaces in sysfs files

[Daniel Drake]

Hi,

I have met a minor issue when writing udev rules.

Some text-like files in /sys have a load of spaces appended onto the text.

Example below, part of the udevinfo for my camera (notice the model field):

follow the class device's "device"
   looking at the device chain at 
'/sys/devices/pci0000:00/0000:00:02.1/usb3/3-3/3-3:1.0/host0/0:0:0:0':
     BUS="scsi"
     ID="0:0:0:0"
     SYSFS{detach_state}="0"
     SYSFS{max_sectors}="240"
     SYSFS{device_blocked}="0"
     SYSFS{queue_depth}="1"
     SYSFS{type}="0"
     SYSFS{scsi_level}="3"
     SYSFS{vendor}="        "
     SYSFS{model}="USB 2.0M DSC    "
     SYSFS{rev}="1.00"
     SYSFS{online}="1"

Second example, an iPod:
http://marc.theaimsgroup.com/?l=gentoo-user&m\x107773927301652&w=2

Of course, udevinfo makes it nice and clear that the extra spaces are there. 
But if you are simply cat'ing the files in /sys its not that obvious.

My questions:

1. Should these spaces be here? Are devices really identifying themselves with 
spaces on the end? Or is this an issue with sysfs/similar.

2. Should udev trim whitespace from the end of SYSFS{..} values (files), so 
that keys such as
   SYSFS{model} = "iPod"
would match a file containing
   "iPod            "

If the above behaviour is implemented, I would suggest having a second key 
type, SYSFS_RAW{..} where whitespace is not trimmed. I am prepared to write a 
patch for this.

Daniel.


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Re: Excess spaces in sysfs files

[Kay Sievers]

On Wed, 2004-02-25 at 22:25, Daniel Drake wrote:
> 1. Should these spaces be here? Are devices really identifying themselves with 
> spaces on the end? Or is this an issue with sysfs/similar.

It's common. Seems like vendors are just filling fixed length fields.
A lot of fields are 8 characters total length.

> 2. Should udev trim whitespace from the end of SYSFS{..} values (files), so 
> that keys such as
>    SYSFS{model} = "iPod"
> would match a file containing
>    "iPod            "
> 
> If the above behaviour is implemented, I would suggest having a second key 
> type, SYSFS_RAW{..} where whitespace is not trimmed. I am prepared to write a 
> patch for this.

Hey, udevinfo is so cute :)
I don't like the idea to try to be smart with the matching, but if we
really want this, I prefer to have it configurable in the config file. 


thanks,
Kay




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Re: Excess spaces in sysfs files

[Greg KH]

On Wed, Feb 25, 2004 at 09:25:16PM +0000, Daniel Drake wrote:
> 1. Should these spaces be here? Are devices really identifying themselves 
> with spaces on the end? Or is this an issue with sysfs/similar.

This is a device issue.  Seems like a lot of them have spaces in odd
places.  Nothing sysfs or udev can do about it.

Go complain to the device manufacturer :)

> 2. Should udev trim whitespace from the end of SYSFS{..} values
> (files), so that keys such as
>   SYSFS{model} = "iPod"
> would match a file containing
>   "iPod            "

No, I don't think so.  That's one reason udevinfo was created to show
you that those spaces are really there.

thanks,

greg k-h


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