Re: [PATCH] USB: Add usbfs ioctl to get the frame number

On Mon, Apr 16, 2007 at 03:55:50PM -0400, Alan Stern wrote:
> From: Danny Budik <[email protected]>
> 
> This patch (as899) adds a new ioctl to usbfs: USBDEVFS_GETFRAMENUM.
> It allows user programs to obtain the current Start-Of-Frame number on
> a USB bus.

But who needs this?

> Note that the values returned by the get_frame method in the various
> host controller drivers are not consistent.

As this number is not consistent, why would exporting it be useful?

> They should be adjusted
> so that they provide the actual frame number as it appears on the bus;
> that is, a number incrementing by one every millisecond, ranging from 0
> to 2047.  That will have to be done separately; it interacts with the
> start_frame values used for submitting Isochronous URBs.

So the current usb_get_current_frame_number() function isn't really
working properly for the 1 in-kernel user today (the other 3 usages are
just in debug printks)?

thanks,

greg k-h

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