linux-kernel - Re: [PATCH 1/2] driver core: emit uevents when device is bound to a driver

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Date:   Mon, 13 Feb 2017 04:07:01 -0800
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH 1/2] driver core: emit uevents when device is bound to a
 driver

On Sun, Feb 12, 2017 at 04:36:18PM -0800, Dmitry Torokhov wrote:
> Majority of standard for a subsystem device attributes are created at the
> same time devices are created, before KOBJECT_ADD uevent is emitted by the
> driver core. This means that attributes are there when userspace is
> notified about new device appearance.
> 
> However many drivers create additional driver-specific device attributes
> when binding to the device, to provide userspace with additional controls,
> and such attributes may not be there yet when userpsace receives
> KOBJECT_ADD event.

How about we fix those drivers instead?

Are you going to change userspace (i.e. libudev) to refresh with this
new kobject uevent type?

The 'groups' field for drivers should handle this, but yes, there are
some subsystems that don't really do it, and there are drivers that like
to add random sysfs files to their device's directories which I would
argue is the correct solution here, but you don't like this, because you
say:

> Changing the drivers to introduce intermediate "dummy" device as a
> container for such attributes would be wasteful, and in many cases,
> braking our sysfs ABI.

I'd argue that you are adding random sysfs files to random device types
(i.e. a PCI device gets a random set of sysfs files just depending on
what driver bound to it.)  And that's wrong, and is why classes were
created.

Is there a specific type of devices that you have that you wish to fix
up using this new uevent type?

thanks,

greg k-h