From: Trent Piepho Date: Sun, 19 Aug 2007 08:05:54 +0000 (-0300) Subject: V4L/DVB (6042): b2c2-flexcop: fix Airstar HD5000 tuning regression X-Git-Tag: v2.6.23-rc4~23^2~1 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=6175e487e314385e37f06448847e4c46c20edb44;p=linux-2.6 V4L/DVB (6042): b2c2-flexcop: fix Airstar HD5000 tuning regression Git changeset 6bdcc6e6dbab8daffd05e5026486f34ba41a6c72 dropped the stand-alone lgh06xf module, whose functionality was absorbed into the dvb-pll module. However, there was a minor difference between the code in lgh06xf and dvb-pll, which caused a regression in b2c2-flexcop devices using the LG-H06xF NIM. dvb-pll will probe for the presence of an i2c pll chip by performing a single byte read, the lgh06xf driver did not do this. Unfortunately, the code in flexcop-i2c.c does not currently support 1 byte or 0 byte reads as a probe. Such probes with the current code will always fail. In order to work around this problem, and restore proper functionality of the Airstar HD5000 device, this hack was created to make the probe appear to succeed. The single byte read in dvb_pll_attach is the only place where such a probe would ever occur, so this change is safe, and will not affect any other devices. Of course, if one knew how to actually perform the read operation, it would be better to go that route. In the meantime, however, we must apply this workaround, in order to prevent the regression that causes tuning to fail on the Airstar HD5000 ATSC device. Thanks to Jarod Wilson, who had originally reported this regression, and to Geoffrey Hausheer, whose original workaround patch led us to find the actual cause of the problem. Signed-off-by: Trent Piepho Cc: Geoffrey Hausheer Acked-by: Jarod Wilson Signed-off-by: Michael Krufky Signed-off-by: Mauro Carvalho Chehab --- diff --git a/drivers/media/dvb/b2c2/flexcop-i2c.c b/drivers/media/dvb/b2c2/flexcop-i2c.c index 02a0ea6e1c..6bf858a436 100644 --- a/drivers/media/dvb/b2c2/flexcop-i2c.c +++ b/drivers/media/dvb/b2c2/flexcop-i2c.c @@ -135,6 +135,13 @@ static int flexcop_master_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs struct flexcop_device *fc = i2c_get_adapdata(i2c_adap); int i, ret = 0; + /* Some drivers use 1 byte or 0 byte reads as probes, which this + * driver doesn't support. These probes will always fail, so this + * hack makes them always succeed. If one knew how, it would of + * course be better to actually do the read. */ + if (num == 1 && msgs[0].flags == I2C_M_RD && msgs[0].len <= 1) + return 1; + if (mutex_lock_interruptible(&fc->i2c_mutex)) return -ERESTARTSYS;