On Sat, 16 Jan 2010, hermann pitton wrote: > Am Freitag, den 15.01.2010, 17:27 -0800 schrieb Trent Piepho: > > On Sat, 16 Jan 2010, hermann pitton wrote: > > > Am Dienstag, den 12.01.2010, 04:13 +0100 schrieb hermann pitton: > > > > > gpio-sysfs creates > > > > > /sys/class/gpio/export > > > > > /sys/class/gpio/import > > > > > but no gpio<n> entries so far. > > > > The saa713x driver predates the generic gpio layer by years and years, so > > it doesn't use it. It also doesn't need to use it. Since the gpios are > > managed by the saa713x driver, and they also used by the saa713x driver, > > there is no need to interface two different drivers together. There are > > tons of drivers for devices that have gpios like this, but they don't use > > the gpio layer. > > > > But with gpio access via sysfs for generic gpios, there is something useful > > about having the saa713x driver support generic gpios. IIRC, somehow wrote > > a gpio only bt848 driver that didn't do anything but export gpios. > > > > In order to do this, you'll have to write code for the saa7134 driver to > > have it register with the gpio layer. I think you could still have the > > saa7134 driver itself use its gpio directly. That would avoid a > > performance penalty in the driver. > > Thanks for more details, but I'm still wondering what pins ever could be > interesting in userland, given that they are all treated such different > per device, and we count up to 200 different boards these days. There are some cards for intended for survilence or embedded applications that have headers on them to connect things to the GPIOs. Like alarms or camera controllers and stuff like that. The GPIO only bttv driver was created by someone who just soldered a bunch of wires on a cheap bt848 card, you can get them for just a few dollars, as it was a cheap and easy way to get a bunch of gpios in a pc. See his page here http://www.bu3sch.de/joomla/index.php/bt8xx-based-gpio-card There are cards you can get that just have GPIOs, but they end up being rather expensive. Here's one: http://www.acromag.com/parts.cfm?Model_ID=317&Product_Function_ID=4&Category_ID=18&Group_ID=1 Way fancier than a tv card, but it's $600. I think if I was doing the coding, I'd add a field in the card description for what GPIOs should be exported. I.e., which ones have an external header. Maybe in addition to, or instead of, I'd have a module option that would cause GPIOs to be exported. A bitmask of which to export would be enough. -- 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
