On Wed, 2011-01-19 at 16:14 -0500, Ben Dooks wrote:
> On Wed, Jan 19, 2011 at 01:26:37PM -0800, Guenter Roeck wrote:
> > Signed-off-by: Guenter Roeck <[email protected]>
[ ... ]
> > +/* Structure to hold all of our device specific stuff */
> > +struct i2c_diolan_u2c {
> > + struct usb_device *usb_dev; /* the usb device for this device */
> > + struct usb_interface *interface;/* the interface for this device */
> > + struct i2c_adapter adapter; /* i2c related things */
> > + int olen; /* Output buffer length */
> > + int ocount; /* Number of enqueued messages */
> > + u8 obuffer[DIOLAN_OUTBUF_LEN]; /* output buffer */
> > + u8 ibuffer[DIOLAN_INBUF_LEN]; /* input buffer */
>
> you should cache-line align the buffers to avoid any problems with
> dma-vs-cache, etc.
>
There are several other drivers which don't cache-align the buffers used
with usb_bulk_msg(). Do those all have potential problems, or is this
only relevant for optimization ?
If it is just for optimization, I'd argue that the speed here is so slow
that it won't make much of a difference, if any, if the buffers were
aligned.
Thanks,
Guenter
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