On 30/08/2017 05:00, Wolfram Sang wrote:
The speed comes from an ACPI entry describing an i2c client,
any compliant i2c client must at least support 100KHz, right ?
Well, due to flaky board design, you may not be able to utilize the max
speed because of interferences etc even if the devices would support it.
Such knowledge of flaky boards could be encoded in the ACPI tables, or?
But probably not in the client device, hmmm...
Alternatively I could wrap the entire round-down for loop in
an if (acpi_speed) {} block.
I don't know enough about real-world ACPI tables to suggest a best
practice here. I just wanted to add that busses < 100 kHz are legal from
how I read the specs.
Oh well, Jarkko liked the patch, so let's all sleep over this patch and
if nothing else comes up, I'll apply it tomorrow or so...
My understanding is 100k is what the client must support.
But sometimes buses need to be run slower.
Particularly when using range extenders.
eg: I have an i2c bus running over a 10m cable that needs to run at about 40k
to be reliable.
--
Regards
Phil Reid
