Re: [lm-sensors] ACPI reads wrong temperature after loading

[Jean Delvare <khali@linux-fr.org>]

On Sat, 1 Nov 2008 16:28:40 +0100, Markus Rechberger wrote:
> On Sat, Nov 1, 2008 at 10:39 AM, Jean Delvare <khali@linux-fr.org> wrote:
> > It would help if I could see the source code of module em28xx_cx25843,
> > but unfortunately I have no idea where that driver lives. Markus?
> 
> http://mcentral.de/hg/~mrec/em28xx-new/file/ca209b1d4076/cx25843/em28xx-cx25843.c

This driver only attaches to (7-bit) address 0x44, while the lm90
driver probes for devices at 0x4c and 0x4d. So I have to admit I am
surprised that loading both drivers leads to the same result.

One note about the em28xx-cx25843 driver: it doesn't check for the
right i2c adapter functionality flags. The driver makes use of raw I2C
transactions to read from and write to the device, so it should check
for I2C_FUNC_I2C, but instead of that I see the following code:

   566 	/* Check if the adapter supports the needed features */
   567 	if (!i2c_check_functionality
   568 			(adapter,
   569 			 I2C_FUNC_SMBUS_READ_BYTE |
   570 			 I2C_FUNC_SMBUS_WRITE_BYTE_DATA))
   571 		return 0;

This is incorrect and should be fixed.

Another thing that should be fixed in this driver is the use of a
"template" i2c_client. This is inefficient in terms of performance,
disk space and memory so it should be avoided. Just setting fields
individually is much better.

-- 
Jean Delvare

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