How to write driver that needs to call another driver?
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From: Stanislav Brabec on 26 Jan 2010 16:10 My Zaurus SL-C3200 PDA needs a driver that needs to call another driver from another part of the device tree: MAX1111 (4 channel A/D) is connected to several other pieces of hardware (audio player remote keyboard, battery voltage, battery temperature, external power voltage). Battery power and charging management needs to read values from MAX1111 during. Also Remote Keyboard input device needs to read MAX1111. But both drivers also need dedicated GPIO that are allocated on Scoop chip (different part of the platform device tree). What is the best way to implement it? Now it is implemented by a hardcoded static reference. This does not work well and breaks on suspend. MAX1111 goes to sleep first and attempt to set-up offline charging fails (see below). I need to make sure, that MAX1111 is going to suspend after the battery management and after the audio remote driver (not yet in vanilla) and resumes before them. What is the best way to implement it? Well, in fact, the problem is even worse: Spitz has a dumb charging management. CPU has to wake-up each few minutes, check the battery, adjust charging parameters and continue in sleeping. That is why I either need to disable sleeping of SPI and MAX1111 or temporarily wake up SPI and MAX111 without going to resume completely. Is something like this possible? It was working in past (linux-2.6.26) - MAX1111+SPI driver was hardcoded into power management and when SPI was probably never suspended. Now it obviously cannot work. Thanks. PM: suspend of devices complete after 549.298 msecs PM: late suspend of devices complete after 0.359 msecs max1111 spi2.2: spi_sync failed with -108 max1111 spi2.2: spi_sync failed with -108 max1111 spi2.2: spi_sync failed with -108 max1111 spi2.2: spi_sync failed with -108 max1111 spi2.2: spi_sync failed with -108 sharpsl-pm sharpsl-pm: Error: AC check failed: voltage -108. sharpsl-pm sharpsl-pm: Offline Charger: Error occurred. sharpsl-pm sharpsl-pm: Charging Error! PM: early resume of devices complete after 0.255 msecs ________________________________________________________________________ Stanislav Brabec http://www.penguin.cz/~utx -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: John Stoffel on 26 Jan 2010 16:50 Stanislav> My Zaurus SL-C3200 PDA needs a driver that needs to call Stanislav> another driver from another part of the device tree: Stanislav> MAX1111 (4 channel A/D) is connected to several other Stanislav> pieces of hardware (audio player remote keyboard, battery Stanislav> voltage, battery temperature, external power voltage). Stanislav> Battery power and charging management needs to read values Stanislav> from MAX1111 during. Also Remote Keyboard input device Stanislav> needs to read MAX1111. Stanislav> But both drivers also need dedicated GPIO that are Stanislav> allocated on Scoop chip (different part of the platform Stanislav> device tree). Stanislav> What is the best way to implement it? By no means am I a driver expert or writer, but from what I recall in the past when such questions came up is for you to write a low level core driver, which binds to the device, and then exposes that various interfaces you want to bind to for other devices to talk to. This gets the ref counting right, and lets you know when something is accessing the MAX1111, so that suspend and such happen in the correct order. Look through the lkml archives for previous answers. I'm sure Greg will have a better answer and a pointer to an example driver to look at. Cheers, John -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
From: Russ Dill on 27 Jan 2010 13:30
Stanislav Brabec <utx <at> penguin.cz> writes: > > My Zaurus SL-C3200 PDA needs a driver that needs to call another driver > from another part of the device tree: > > MAX1111 (4 channel A/D) is connected to several other pieces of hardware > (audio player remote keyboard, battery voltage, battery temperature, > external power voltage). > > Battery power and charging management needs to read values from MAX1111 > during. Also Remote Keyboard input device needs to read MAX1111. > > But both drivers also need dedicated GPIO that are allocated on Scoop > chip (different part of the platform device tree). > GPIO already has a generic API that can be used. I've had similar problems with I2C devices. I've always implemented as adding in .command support to the I2C driver in question, using i2c_use_client and then try_module_get. I'm not sure if it is the proper way of doing things, it's always bugged me that there doesn't seem to programatically access things like I2C eeproms and HW monitoring devices. They seem to only be exposed though sysfs. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo(a)vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ |