Messages in this thread | ![/](/images/icornerl.gif) | | From | Måns Rullgård <> | Subject | Re: [PATCH 2/3] i2c: xlr: fix extra read/write at end of rx transfer | Date | Tue, 15 Dec 2015 12:48:06 +0000 |
| |
Wolfram Sang <wsa@the-dreams.de> writes:
> On Mon, Nov 02, 2015 at 02:03:37AM +0000, Mans Rullgard wrote: >> The BYTECNT register holds the transfer size minus one. Setting it >> to the correct value requires a dummy read/write only for zero-length >> transfers as it is impossible to request one from the hardware. If a >> zero-length transfer is requested, changing the length to 1 and setting >> "buf" to a dummy location allows making the main loops less convoluted. >> >> In other words, this patch makes the driver transfer the number of bytes >> requested unless this is zero, which is not supported by the hardware, >> in which case one byte is transferred instead. > > Uh, this is wrong, zero byte should really not transfer anything. We > need to fix that and bail out, so probably something like > > if (!len) > return -EOPNOTSUPP;
So the existing driver is wrong to allow it. Makes sense to drop that.
> Also, the xlr_func() should mask out I2C_FUNC_SMBUS_QUICK.
OK.
> Other than that, the patch looks good to me. > > Out of curiosity, your first driver had the registers 32bit apart. Now > you can deal with 8bit. Is this configurable on this SoC?
It's all 32 bits. The XLR driver uses a u32 * to access the registers.
-- Måns Rullgård
| ![\](/images/icornerr.gif) |