Em 30-09-2010 19:07, Michael Krufky escreveu: > On Thu, Sep 30, 2010 at 6:00 PM, Antti Palosaari <crope@xxxxxx> wrote: >> On 09/30/2010 09:52 PM, Michael Krufky wrote: >>> >>> On Tue, Sep 28, 2010 at 2:46 PM, Mauro Carvalho Chehab >>> <mchehab@xxxxxxxxxx> wrote: >>>> >>>> By default, tda18271 tries to optimize I2C bus by updating all registers >>>> at the same time. Unfortunately, some devices doesn't support it. >>>> >>>> The current logic has a problem when small_i2c is equal to 8, since there >>>> are some transfers using 11 + 1 bytes. >>>> >>>> Fix the problem by enforcing the max size at the right place, and allows >>>> reducing it to max = 3 + 1. >>>> >>>> Signed-off-by: Mauro Carvalho Chehab<mchehab@xxxxxxxxxx> >>> >>> This looks to me as if it is working around a problem on the i2c >>> master. I believe that a fix like this really belongs in the i2c >>> master driver, it should be able to break the i2c transactions down >>> into transactions that the i2c master can handle. >>> >>> I wouldn't want to merge this without a better explanation of why it >>> is necessary in the tda18271 driver. It seems to be a band-aid to >>> cover up a problem in the i2c master device driver code. >> >> Yes it is I2C provider limitation, but I think almost all I2C adapters have >> some limit. I suggest to set param for each tuner and demod driver which >> splits reads and writes to len adapter can handle. I did that for tda18218 >> write. >> >> But there is one major point you don't see. It is not simple to add this >> splitting limit to the provider. Provider does not have knowledge which is >> meaning of bytes it transfers to the bus. Without knowledge it breaks >> functionality surely in some point. There is commonly seen 1, 2 and 4 byte >> register address and same for register values. Also some chips like to send >> data as register-value pairs. > > Yes, I understand. We will likely merge Mauro's patch, I just want to > test it on my own hardware first, and I'd like to verify the cx231xx > i2c xfer limit issue that Mauro is reporting. I'll try to get back to > this early next week, or hopefully over this weekend. Feel free to test. Just remember that all Hauppauge devices at Devin's polaris4 tree uses I2C Channel #1. This seems to be the default on all Conexant SDK also. The device I'm working with has the tuner at channel #2, and the ISDB-T demod at channel #1. So, the limits may differ. On my device, everything seem to work fine with max size = 4 (both analog and digital modes). Cheers, Mauro -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
