[fpc-pascal] USB Human Interface Devices

Johann Glaser Johann.Glaser at gmx.at
Mon Aug 12 22:10:37 CEST 2019 

Hi!

Am Sonntag, den 11.08.2019, 19:13 -0400 schrieb James Richters:
> Thank you for the help.  I made most of the changes you recommend and
> I was able to get it to compile,  the only one I had trouble with was
> If I take out the ^ from:
>        if (EP^.bmAttributes and LIBUSB_TRANSFER_TYPE_MASK =
>  LIBUSB_TRANSFER_TYPE_INTERRUPT) and
>           (EP^.bEndpointAddress and LIBUSB_ENDPOINT_DIR_MASK <> 0)
> then
>
> So it looks like this:
>        if (EP.bmAttributes and LIBUSB_TRANSFER_TYPE_MASK =
>  LIBUSB_TRANSFER_TYPE_INTERRUPT) and
>           (EP.bEndpointAddress and LIBUSB_ENDPOINT_DIR_MASK <> 0)
> then
>
> I get a compiler error:
> libusboop.pas(1168,14) Error: Illegal qualifier
> libusboop.pas(1168,14) Fatal: Syntax error, ")" expected but
> "identifier BMATTRIBUTES" found
> libusboop.pas(0) Fatal: Compilation aborted
>
> With the ^ in it compiles anyway... I don't know how to adjust the
> format to not have the ^
>
> I have not tried to do anything with TLibUsbPseudoHIDInterface yet, I
> was just trying to get libusboop.pas to compile, and be able to still
> run the previous examples.
>
> I've updated my repository at
> https://github.com/Zaaphod/pas-libusb/tree/Test
>
> Let me know if I should do something different with the ^ above, or
> if you see anything else I missed.

Ah, I see. You declared EP as Plibusb_endpoint_descriptor (i.e., the
pointer to an endpoint descriptor record), while in the original code
it is a USBEndpointDescriptor (i.e., the record itself).

Your version is more memory efficient but uses "ugly pointer-
arithmetic" by taking the address of an array element. However, just
keep it as you implemented it.

While reviewing your changes, I found a few small things.

Could you please keep the indenting and coding style as the existing
code? This is especially for the constant and type declarations around
TLibUsbPseudoHIDInterface (IIRC the keywords Type and Const should
start at character 1, therefore you also should un-indent the 6+3
constants and the P/THIDReport record (except its final "End;" by 2
spaces.

Secondly, in your improved TLibUsbInterface.FindEndpoint, please revert
the capitalization and indenting changes (i.e., capital "Function",
"For", ..., and "do" and "then" in the same line, ... IMHO the only
changed lines in comparison to the original code should be the extra
variable EP, its assignment without range checks, and its use in
MatchFunc and Exit.

And thirdly, you introduced a class type TLibUsbInterruptInEndpoint,
which is IMHO unused. If its so, please remove it. I like to avoid
clutter. :-)

Apart form these cosmetic things, thank you very much for your effort!
I'm looking forward hearing from you your success when accessing a HID
device (or call for help :-) ).

Thanks
  Hansi

> -----Original Message-----
> From: fpc-pascal <fpc-pascal-bounces at lists.freepascal.org> On Behalf
> Of Johann Glaser
> Sent: Sunday, August 11, 2019 4:16 PM
> To: fpc-pascal at lists.freepascal.org
> Subject: Re: [fpc-pascal] USB Human Interface Devices
>
> Hi!
>
> Am Samstag, den 10.08.2019, 17:50 -0400 schrieb James Richters:
> > I'm making an attempt to copy TUSBPseudoHIDInterface into
> > libusboop.pas.  I've made the recomended name changes and then
> > tried
> > to compile it.  Some things I found like the names changing from
> > things like
> >
> > PUSBInterfaceDescriptop to Plibusb_interface_descriptor
>
> OK, there are two things. Names directly from libusb-1.0 (as used in
> libusb.pas) should be identical to the original C code, i.e.,
> Plibusb_interface_descriptor as you've written.
>
> The second thing are the classes in the OOP wrapper in libusboop.pas.
> Please use CamelCase for them, e.g., TLibusbPseudoHIDInterface.
>
> > are pretty obvious, but just taking a guess on other things like:
> >
> >  changing:
> >       if (EP.bmAttributes and USB_ENDPOINT_TYPE_MASK =
> > USB_ENDPOINT_TYPE_INTERRUPT) and
> >          (EP.bEndpointAddress and USB_ENDPOINT_DIR_MASK <> 0) then
> >
> > To:
> >       if (EP^.bmAttributes and LIBUSB_TRANSFER_TYPE_MASK =
> > LIBUSB_TRANSFER_TYPE_INTERRUPT) and
> >          (EP^.bEndpointAddress and LIBUSB_ENDPOINT_DIR_MASK <> 0)
> > then
>
> Yes, very good, thanks!
>
> Whether EP is a pointer (--> EP^.bmAttributes) or a record
> (EP.bmAttributs) just depends on the usage in the code. As I see in
> usb.pas in line 846, in TUSBPseudoHIDInterface.Create, it is actually
> the record, so you should stay without the '^'.
>
> > Based on looking at something similar in libusbutil... but I'm not
> > sure it's right at all.... I'm not sure if USB_ENDPOINT_TYPE_MASK
> > was
> > really changed to LIBUSB_TRANSFER_TYPE_MASK or if something else
> > happened.  But at least it compiles...
>
> You translated it correctly.
>
> > but now I've hit a few items that I just don't know what to do
> > with.    I can't find anything similar to get a reference from:
> >
> > libusboop.pas(1198,28) Error: Identifier not found "USB_TYPE_CLASS"
>
> Use LIBUSB_REQUEST_TYPE_CLASS.
>
> > libusboop.pas(1199,5) Error: Identifier not found
> > "USB_REQ_HID_SET_REPORT"
> > libusboop.pas(1216,27) Error: Identifier not found "USB_TYPE_CLASS"
> > libusboop.pas(1217,5) Error: Identifier not found
> > "USB_REQ_HID_GET_REPORT"
> > libusboop.pas(1227,23) Error: Identifier not found
> > "HID_REPORT_TYPE_OUTPUT"
>
> Please copy the constants USB_REQ_HID_* and HID_REPORT_* from
> libusb.pas (branch master) lines 248-257 to the interface section of
> libusboop.pas (branch libusb-1.0) directly above the class
> declaration of TLibusbPseudoHIDInterface. Then please rename
> USB_REQ_HID_* to
> LIBUSB_REQUEST_HID_* and HID_REPORT_* to LIBUSB_HID_REPORT_*.
>
> > I've tried things that seem to be in line with other changes, like
> > changing USB_Type_Class to LIBUSB_TYPE_CLASS or spelling out
> > REQUEST
> > instead of REQ which also seems to be done in other places, but
> > still
> > the identifiers are not found... the problem is I have no idea
> > where
> > these identifiers were/are defined.
> >
> > I made a fork in github and a branch called "test"  here:
> > https://github.com/Zaaphod/pas-libusb/tree/Test
>
> Great approach, thanks, then we can use pull requests.
>
> Thanks
>   Hansi
>
> > > Actually you could copy the class TUSBPseudoHIDInterface (plus
> > > the
> > > types THIDReport and TIntrReportFunc) from usb.pas to
> > > libusboop.pas
> > > and change everything necessary.
> > > At least one difference is that all names change from TUSB* to
> > > TLibUsb*. I'm sure there are more, but I don't know by heart.
> >
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