Re: loading firmware while usermodehelper disabled.

On 02/01/12 20:48, Linus Torvalds wrote:

On Mon, Jan 2, 2012 at 12:41 PM, Jack Stone [off-list ref] wrote:

quoted

What about the case where the firmware that needs to be loaded is on the
USB device that needs the firmware. This can be resolved at boot using
an initrd but at resume time we don't have that.

Quite frankly, caching the firmware will just automagically fix this.

I don't understand why people even bother to talk about USB ID's etc
changing - that is totally irrelevant. We don't look up firmware by
USB ID's anyway.

I agree. The only problem I can see is with the lifetime of the
firmware. If we have a generic USB driver that looks after (for example)
all USB disks then we do not want to add the knowedge to it for each
individual vendors firmware.

For example:

	1/ Plug in device, registers as a bootstrap device
	2/ Load firmware into device (and put firmware in cache)
	3/ Device disconnects and reconnects with new USB id
	4/ Generic driver takes over as it recognizes the new id

The problem comes with knowing when to put the firmware - how do we tell
the generic driver that that device has firmware that might need to be
freed on disconnect. I don't know enough about USB to know if we can
tell if the same device has reconnected due to firmware being loaded or
if it was simply unplugged and a new device plugged in.

Hope this makes sense,

Jack