On 29/04/2012, at 4:14 AM, Uwe Bonnes wrote:
>>>>>> "Daniel" == Daniel Kirkham <dk2@xxxxxxxxxxxxx> writes:
>
> Daniel> Hi all, I just noticed an inconsistency in the handling of the
> Daniel> max_power EEPROM value while writing a short program to
> Daniel> reprogram my FT2232.
>
> Daniel> In ftdi_eeprom_build (line 2580 of ftdi.c):
>
> Daniel> output[0x09] = eeprom->max_power>>1;
>
> Daniel> Whereas: in ftdi_eeprom_decode (line 3051 of ftdi.c):
>
> eeprom-> max_power = buf[0x09];
>
> Daniel> and further down in ftdi_eeprom_decode (line 3267):
>
> Daniel> fprintf(stdout, "Bus Powered: %3d mA%s",
> Daniel> eeprom->max_power * 2,
>
> Daniel> and ftdi_get_eeprom_value (line 3448)
>
> Daniel> *value = ftdi->eeprom->max_power;
>
> Daniel> and ftdi_set_eeprom_value (line 3635)
>
> ftdi-> eeprom->max_power = value;
>
> Daniel> So, with the exception of line 2580, the value being passed
> Daniel> around is the power requirement expressed as half the number of
> Daniel> milliamperes (mA) required by the device, and that line 3267
> Daniel> correctly translates this for presentation purposes. This is
> Daniel> consistent with the way power units are specified within the USB
> Daniel> protocols (ie. each unit is 2mA).
>
> Daniel> On this basis, the bit-shift division in line 2580 should be
> Daniel> removed: 2580: output[0x09] = eeprom->max_power;
>
> Daniel> Alternatively, if the API defines that max_power should be
> Daniel> expressed directly in mA, then lines 3051 and 3267 need to be
> Daniel> adjusted to: 3051: eeprom->max_power = buf[0x09] * 2; 3267:
> Daniel> fprintf(stdout, "Bus Powered: %3d mA%s", eeprom->max_power,
>
> Daniel> Given these changes may break some usage, perhaps this needs to
> Daniel> be discussed before patching the library one way or the other.
>
> Thanks for catching this error. Getting it consistant probably doesn't
> break much but mixes more. I propose having eeprom->max_power in mA.
>
> Will you prepare a patch?
I'm in the midst of a very busy week, so will look at preparing a patch over
the coming weekend.
Daniel
>
> Bye
> --
> Uwe Bonnes bon@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
> --------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
>
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