linux-kernel - Re: [Patch] Increase USBFS Bulk Transfer size

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Date:	Thu, 13 Oct 2011 15:04:39 +0530
From:	Manu Abraham <abraham.manu@...il.com>
To:	Markus Rechberger <mrechberger@...il.com>
Cc:	Greg KH <gregkh@...e.de>, Alan Stern <stern@...land.harvard.edu>,
	USB list <linux-usb@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch] Increase USBFS Bulk Transfer size

> yes the PID is 0x1fff which are null packets over there, so those ones are okay.
> Main point is it works and it would even comply with certain HW specs (the other
> device points out about 256*188 bulk transfer buffer sizes.
>
> Now it would be the time for some people to open their eyes and get
> that patch in.

Call me dumb, but it still defies my logic why there would be stream
corruption with a smaller buffer size, if the driver is handling the
stream correctly.

I can probably imagine that there could be a likely chance, user space
would have to poll more often in case with smaller buffers, while
making it larger you increase the latency of the stream; that being a
double edged blade.

> The maximum transfer buffer size was derived from our other device which can
> do the flexible setting. According to the specification it is no magic value.

So, with your single device, if you were to make changes to some
"magical constants"; and tomorrow if someone wants to have
modifications again, what would you do ? If that change is a must,
maybe it should be configurable in some way, rather than having
another fixed magical number.

Regards,
Manu
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