Hi Per,
On Thu, 26 May 2011 11:27:27 +0200, Per Dalén wrote:
> Changed according to the suggestions from Guenter Roeck:
>
> * Check the manufacturer ID directly. Fastens the test if it's not a
> Maxim chip.
> * Read the other non-existing registers after the manufacturer ID.
THis is better but I'm not completely happy yet.
> This patch adds detection of MAX6642 to sensors-detect.
>
> Signed-off-by: Per Dalen <per.dalen@xxxxxxxxxxxx>
> ---
>
> --- prog/detect/sensors-detect (revision 5975)
> +++ prog/detect/sensors-detect (working copy)
> @@ -848,6 +848,11 @@
> i2c_addrs => [0x2c, 0x2e, 0x2f],
> i2c_detect => sub { max6639_detect(@_); },
> }, {
> + name => "Maxim MAX6642",
> + driver => "max6642",
> + i2c_addrs => [0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f],
Better written: [0x48..0x4f]
> + i2c_detect => sub { max6642_detect(@_); },
> + }, {
> name => "Maxim MAX6655/MAX6656",
> driver => "max6655",
> i2c_addrs => [0x18..0x1a, 0x29..0x2b, 0x4c..0x4e],
> @@ -5779,6 +5784,36 @@
> return 6;
> }
>
> +# Chip to detect: MAX6642
> +# Registers used:
> +# 0x02: Status register
> +# 0x03: Configuration register
> +# 0xfe: Manufacturer ID
> +# 0x04,0x06,0xff: No registers
> +# We use the 0x04,0x06 and 0xff addresses (unused) to improve the
Space after comma please.
> reliability.
Please disable line wrapping in your e-mail client before sending patches.
> +# These are not real registers and will always return the last returned
> value.
> +# This isn't documented.
> +sub max6642_detect
> +{
> + my ($file, $addr) = @_;
> + my ($man_id, $conf, $status);
> +
> + $man_id = i2c_smbus_read_byte_data($file, 0xfe, NO_CACHE);
> + return unless $man_id == 0x4d; # Maxim
> + return if i2c_smbus_read_byte_data($file, 0x04, NO_CACHE) != $man_id;
> + return if i2c_smbus_read_byte_data($file, 0x06, NO_CACHE) != $man_id;
> + return if i2c_smbus_read_byte_data($file, 0xff, NO_CACHE) != $man_id;
> + $status = i2c_smbus_read_byte_data($file, 0x02, NO_CACHE);
At this point you should check the unused status bits immediately (so
that you can exit if they don't meet the expectations.) Then you should
read non-registers 0x04, 0x06 and 0xff again. This is the only reliable
way to make sure that there are no registers at these addresses. It is
perfectly possible (though unlikely) that a given chip does have values
0x4d for all of registers 0x04, 0x06, 0xfe and 0xff.
See max6657_detect() for an example.
> + $conf = i2c_smbus_read_byte_data($file, 0x03, NO_CACHE);
NO_CACHE is not needed here, as this register 0x03 does exist. Only use
NO_CACHE when you really need it, it's expensive!
> +
> + # Bit 5, 3, 1 and 0 should be zero
> + return unless ($status & 0x2b) == 0x00;
> + # The 4 lower bits should be zero
> + return unless ($conf & 0x0f) == 0x00;
> +
> + return 6;
> +}
> +
> sub max6655_detect
> {
> my ($file, $addr) = @_;
--
Jean Delvare
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