Hi,
Based on what we found in
http://lists.freebsd.org/pipermail/freebsd-current/2008-December/001052.html
I hacked up the following patch to uftdi which allows the recv/xmit
buffer size to be tuned at bootup time. This allows our app which is
low speed (1200bps), but very timing sensitive to work using a usb
serial adaptor based on the uftdi chipset. For us, adding
hint.uftdi.0.buffersize="9" to /boot/device.hints does the trick.
Is there a better way to do this ? Are there any other side effects
anyone can think of ?
--- sys/dev/usb/uftdi.c.orig 2008-12-09 11:47:02.000000000 -0500
+++ sys/dev/usb/uftdi.c 2008-12-09 11:47:05.000000000 -0500
@@ -198,6 +198,7 @@
usb_interface_descriptor_t *id;
usb_endpoint_descriptor_t *ed;
int i;
+ unsigned int ivar;
usbd_status err;
struct ucom_softc *ucom = &sc->sc_ucom;
DPRINTFN(10,("\nuftdi_attach: sc=%p\n", sc));
@@ -353,11 +354,27 @@
ucom->sc_portno = FTDI_PIT_SIOA;
else
ucom->sc_portno = FTDI_PIT_SIOA + id->bInterfaceNumber;
- /* bulkin, bulkout set above */
- ucom->sc_ibufsize = UFTDIIBUFSIZE;
- ucom->sc_obufsize = UFTDIOBUFSIZE - sc->sc_hdrlen;
- ucom->sc_ibufsizepad = UFTDIIBUFSIZE;
+ /* For certain low speed / timing sensitive applications
having the buffers too large causes
+ data to be stuck in the queue too long. By adding a
tuneable, users can lower the buffer
+ size to what works for their application
+ */
+
+ if (!resource_int_value(
+ "uftdi", device_get_unit(ucom->sc_dev), "buffersize",
&ivar) && (ivar > sc->sc_hdrlen && ivar <= UFTDIIBUFSIZE) ) {
+ ucom->sc_ibufsize = ivar;
+ ucom->sc_obufsize = ivar - sc->sc_hdrlen;
+ ucom->sc_ibufsizepad = ivar;;
+ device_printf(ucom->sc_dev, "Setting buffers
to %d\n",ivar);
+ }
+ else
+ {
+ ucom->sc_ibufsize = UFTDIIBUFSIZE;
+ ucom->sc_obufsize = UFTDIOBUFSIZE - sc->sc_hdrlen;
+ ucom->sc_ibufsizepad = UFTDIIBUFSIZE;
+ device_printf(ucom->sc_dev, "Setting buffers
to default of %d\n",UFTDIIBUFSIZE);
+
+ }
ucom->sc_opkthdrlen = sc->sc_hdrlen;
---Mike
--------------------------------------------------------------------
Mike Tancsa, tel +1 519 651 3400
Sentex Communications, [EMAIL PROTECTED]
Providing Internet since 1994 www.sentex.net
Cambridge, Ontario Canada www.sentex.net/mike
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