Messages in this thread | | | Date | Wed, 7 Jun 2006 21:06:42 +0300 | From | Alexander Atanasov <> | Subject | Re: [PATCH] I2C block read |
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On Wed, 7 Jun 2006 19:49:43 +0200 Jean Delvare wrote:
> Hi Alexander, > > > When doing i2c block read the lenght is passed as the first > > byte of the buffer, so we must copy it from user otherwise temp is > > uninitialized. > > > --- drivers/i2c/i2c-dev.c.orig 2006-01-04 02:00:00.000000000 > > +0200 +++ drivers/i2c/i2c-dev.c 2006-06-07 > > 19:46:08.000000000 +0300 @@ -337,6 +337,7 @@ > > > > if ((data_arg.size == I2C_SMBUS_PROC_CALL) || > > (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) > > || > > + (data_arg.size == I2C_SMBUS_BLOCK_DATA) || > > (data_arg.read_write == I2C_SMBUS_WRITE)) { > > if (copy_from_user(&temp, data_arg.data, > > datasize)) return -EFAULT; > > Nack. Firstly, your comment says I2C block read, but your code changes > SMBus block read. These are two different transactions. Secondly, for > SMBus block read, the master doesn't ask for a given number of bytes. > Instead, the chip decides and returns the number of (following) bytes > as the first byte of the read part of the transaction. Check the SMBus > specification. > > So your patch is not correct, sorry.
10x. Here is the case: I use SMBus block read with scx200_acb as a bus it uses the lenght which is as i say uninitialized and tries to read a number of random bytes from the board i use. And it doesn't return the lenght as a first byte, so the drivers reads until it gets an oops. Which in turn makes me wonder why with this patch i correcly receive the number of bytes i pass, looking at the driver i can not see that it gets the lenght from the read data. I don't know well SMBus/I2C specs but read with buffer and no lenght doesn't look sane to me. So how should this be fixed?
-- have fun, alex
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