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

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Date:	Wed, 12 Oct 2011 14:36:59 +0200
From:	Markus Rechberger <mrechberger@...il.com>
To:	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: [Patch] Increase USBFS Bulk Transfer size

We have 2 products which can perform better with increased Bulk transfers

Device No. 1:
According to the hardware spec of on of our product
Available Bulk Transfer Size are:
- 188 * n bytes, where n = 1 ~ 256.

Although we can drive that one with 15K as well when setting the HW
register down to it.

Device No. 2
only creates jitter video with Bulk transfer sizes which are below
24064 bytes, no such chipfeature is available
to decrease the bulk transfer size.
http://sundtek.de/images/dtvjitter2.jpg
with transfer size of 24064:
http://sundtek.de/images/gooddata.jpg

The patch takes the features of Device No. 1 into account allowing a
maximum buffer of 48128 bytes.

Those issues have been evaluated with MacOSX and a customized patched
Linux version.
Device No. 2 also corrupts on MacOSX with too small packet sizes,
Windows and Mac are using 24064 bytes.

Default Bulk Transfersize of device No. 1 is around 1-2k which leads
to very high cpu usage, updating it to 15k lowers that one.

View attachment "devio.c.diff" of type "text/x-patch" (336 bytes)