Messages in this thread | | | Date | Tue, 20 Mar 2012 16:32:10 -0700 | From | Nick Dyer <> | Subject | Re: [PATCH 06/20] Input: atmel_mxt_ts - allow writing to object sysfs entry |
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Alan Cox wrote: > On Tue, 13 Mar 2012 20:04:09 +0800 > Daniel Kurtz <djkurtz@chromium.org> wrote: >> Userspace can write a 24-bit value (encoded as a 6 character hex string) >> to the 'object' sysfs entry to modify a single byte of the object table. >> The hex string encodes a 3 bytes, in the following format: > > How is this locked against other users and updates of these table data ? > > I don't see how all the objects and their pointers and size are > guaranteedto always be valid in all the users you have ?
The particular layout of the "objects" on the maxtouch chip only changes if there is a firmware upgrade (or between different models of chip). It's just a convenience to allow bits of functionality to be extended or replaced without getting in a mess of random register in different places, but it's not dynamic.
In terms of arbitrating between different reads/writes - the I2C bus locking will handle most of it. To be entirely correct, I think there should be a mutex so that this interface couldn't be used whilst the chip is resetting, backing up or upgrading firmware.
-- Nick Dyer Software Engineer, ITDev Ltd Hardware and Software Development Consultancy Website: http://www.itdev.co.uk
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