Mark Studebaker wrote:
is there a way to do this solely in i2c-core without having to add support to all the drivers?
Yes and no. In order to support this async operation, the driver cannot block and do things like msleep() or schedule(). It has to start the operation, return, and either let polling or an interrupt drive the continued operation. Thus for async operations the driver has to be modified. However, if async operation is not required, the driver can stay as is.
I've been working on this and will probably have a patch tomorrow. I've modified the piix4 and the i801 drivers, I probably won't do any more myself unless the need arises, since I can't test any others. Note that this still supports the old driver interface, so no drivers need to be rewritten. That way, they only need to be modified if something needs the async interface. So drivers that have an RTC on them or that support IPMI BMCs could be rewritten, but nothing else needs to be done.
I've also noticed a somewhat cavalier attitude in this code with respect to return values. I've cleaned some of that up so return values are not just -1 on error, but are proper errno values. However, I've only fixed the core code and the drivers I've worked on.
Thanks,
-Corey
Corey Minyard wrote:
I have an IPMI interface driver that sits on top of the I2C code. I'd like to get it into the mainstream kernel, but I have a few problems to solve first before I can do that. The I2C code is synchronous and must run from a task context. The IPMI driver has certain operations that occur at panic time, including:
* Storing panic information in IPMI's system event log * Extending the watchdog timer so it doesn't go off during panic operations (like kernel coredumps). * Powering the system off
I can't really put the IPMI SMB interface into the kernel until I can do those operations. Also, I understand that some vendors put RTC chips onto the I2C bus and this must be accessed outside task context, too. I would really like add asynchronous interface to the I2C bus drivers. I propose:
* Adding an async send interface to the busses that does a callback when the operation is complete. * Adding a poll interface to the busses. The I2C core code could call this if a synchronous call is made from task context (much like all the current drivers do right now). For asyncronous operation, the I2C core code would call it from a timer interrupt. If the driver supported interrupts, polling from the timer interrupt would not be necessary. * Add async operations for the user to call, including access to the polling code. * If the driver didn't support an async send, it would work as it does today and the async calls would return ENOSYS.
This way, the bus drivers on I2C could be converted on a driver-by-driver basis. The IPMI code could query to see if the driver supported async operations. And the RTC code could use it, too.
Is this ok with the I2C community? I would do the base work and convert over a few drivers.
Thanks,
-Corey
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