Implement Printer Device Driver

[remiberthoz]

Describe the PR
Implement a printer device driver for USB Printers. The example illustrates receiving data from a host, the device driver as-is is recognized by the generic printer drivers on linux (and I assume, Windows too).

This allows sending binary data to the device, with no specific drivers, using tools like lp -o raw.

Additional context
The example compiles and works on a Pi Pico.

I am not yet sure about integration of the changes in the build toolchain. I have not yet understood if I have to manually edit all the hw/{bsp,mcu}/ file to include the device driver in cmake source lists.

[remiberthoz]

Well I apparently made (at least) one major mistake when moving the code from my local project to the repository fork. The content of printer.h and printer_device.c is the same, leading to (part of) the compilation errors. I'll work on that and the other problems raised by the CI pipeline.

[remiberthoz]

Ok, I'm realizing that I developed this locally against version 0.18.0 but tried to merge it in version 0.20.0. This is not the only problem but I am back on track. I'll see what was changed between the two releases and update the device driver accordingly.

[remiberthoz]

In my terminal, compilation and upload of the printer_to_hid example now correctly yields :

$ cat helloworld.ps  # see helloworld.ps content
  %!PS
  8 selectfont
  (Hello world!) show

$ lp -d TinyUSB_Device -o raw ./helloworld.ps  # print helloworld.ps on the device
  request id is TinyUSB_Device-330 (1 file(s))

$   PS 8 selectfont  Hello world   show  # auto-typed by HID

The last line is automatically typed by the HID device. Only alphanumeric characters are handled by the example program, but other characters could be translated to HID keycodes too. The printer endpoint receives UTF8.

---

CircleCI has caught one remaining [[maybe_unused]] flag that I'll replace with a (void) (in the one-random-make-msp430-large-msp430-gcc test). I believe the other failing tests are not directly related to the printer device class or its example, but to the build toolchain that is not correctly adjusted yet.

[remiberthoz]

Looking forward to your feedback!

I believe I’ve addressed the issues in the sections of code I added. If there’s anything else you'd like me to revisit or any concerns with the implementation, please let me know. I’m happy to make further adjustments.

[github-actions]

Size Difference Report

Because TinyUSB code size varies by port and configuration, the metrics below represent the averaged totals across all example builds.

Note: If there is no change, only one value is shown.

Changes >1% in size

file	.text	.bss	size	% diff
dcd_musb.c	2431 ➙ 2079 (-352)	160	2591 ➙ 2239 (-352)	-13.6%
TOTAL	2431 ➙ 2079 (-352)	160	2591 ➙ 2239 (-352)	-13.6%

Changes <1% in size

No entries.

No changes

file	.text	.rodata	.data	.bss	size	% diff
audio_device.c	2849	0	1248	1673	4518	+0.0%
cdc_device.c	1328	16	19	661	1988	+0.0%
cdc_host.c	6596	487	15	1539	8357	+0.0%
dcd_ch32_usbfs.c	1472	0	0	2444	3916	+0.0%
dcd_ch32_usbhs.c	1648	0	0	448	2096	+0.0%
dcd_ci_fs.c	1925	0	0	1290	3215	+0.0%
dcd_ci_hs.c	1762	0	0	1280	2530	+0.0%
dcd_da146xx.c	3067	0	0	144	3211	+0.0%
dcd_dwc2.c	4101	24	0	263	4387	+0.0%
dcd_eptri.c	2270	0	0	259	2529	+0.0%
dcd_khci.c	1953	0	0	1290	3243	+0.0%
dcd_lpc17_40.c	1470	0	0	648	1794	+0.0%
dcd_lpc_ip3511.c	1463	0	0	264	1639	+0.0%
dcd_mm32f327x_otg.c	1478	0	0	1290	2768	+0.0%
dcd_msp430x5xx.c	1796	0	0	176	1972	+0.0%
dcd_nrf5x.c	2919	0	0	292	3211	+0.0%
dcd_nuc120.c	1093	0	0	78	1171	+0.0%
dcd_nuc121.c	1167	0	0	101	1268	+0.0%
dcd_nuc505.c	0	0	1529	157	1686	+0.0%
dcd_rp2040.c	859	20	604	655	2138	+0.0%
dcd_rusb2.c	2917	0	0	156	3073	+0.0%
dcd_samd.c	1032	0	0	266	1298	+0.0%
dcd_samg.c	1319	0	0	72	1391	+0.0%
dcd_stm32_fsdev.c	2556	0	0	291	2847	+0.0%
dfu_device.c	744	28	712	183	926	+0.0%
dfu_rt_device.c	156	0	134	0	156	+0.0%
dwc2_common.c	582	29	0	0	597	+0.0%
ecm_rndis_device.c	1037	0	1	2272	3310	+0.0%
ehci.c	2761	0	0	5970	7537	+0.0%
fsdev_common.c	180	0	0	0	180	+0.0%
hcd_ch32_usbfs.c	2484	0	0	498	2982	+0.0%
hcd_ci_hs.c	190	0	0	0	190	+0.0%
hcd_dwc2.c	4893	30	0	512	5434	+0.0%
hcd_khci.c	2442	0	0	449	2891	+0.0%
hcd_musb.c	3073	0	0	157	3230	+0.0%
hcd_pio_usb.c	262	0	240	0	502	+0.0%
hcd_rp2040.c	976	73	416	384	1849	+0.0%
hcd_rusb2.c	2923	0	0	245	3168	+0.0%
hcd_samd.c	2220	0	0	324	2544	+0.0%
hcd_stm32_fsdev.c	3282	0	1	420	3703	+0.0%
hid_device.c	1118	44	997	115	1233	+0.0%
hid_host.c	1206	0	0	1250	2456	+0.0%
hub.c	1235	8	8	29	1268	+0.0%
midi_device.c	1127	0	991	589	1714	+0.0%
midi_host.c	1353	7	7	3740	5097	+0.0%
msc_device.c	2503	108	2274	538	3041	+0.0%
msc_host.c	1589	0	0	394	1984	+0.0%
mtp_device.c	1689	22	1449	579	2275	+0.0%
ncm_device.c	1514	28	1408	5830	7358	+0.0%
ohci.c	1942	0	0	2414	4356	+0.0%
rp2040_usb.c	172	75	718	4	969	+0.0%
rusb2_common.c	160	0	16	0	176	+0.0%
tusb.c	416	0	359	3	418	+0.0%
tusb_fifo.c	843	0	477	0	838	+0.0%
typec_stm32.c	820	8	2	12	842	+0.0%
usbc.c	420	2	20	166	608	+0.0%
usbd.c	3177	57	89	276	3518	+0.0%
usbd_control.c	523	0	474	78	600	+0.0%
usbh.c	4374	60	63	954	5415	+0.0%
usbtmc_device.c	2176	24	69	291	2500	+0.0%
vendor_device.c	624	0	530	464	1087	+0.0%
video_device.c	4391	5	1851	472	4855	+0.0%
TOTAL	110617	1155	16721	45349	158053	+0.0%

[HiFiPhile]

Hi, thank you for adding printer driver ! I've just tested that it's working on Windows 11 with a manual driver install, I'll leave my reviews below.

[remiberthoz]

Thank you, I am looking forward to feedback. The tests I could perform on Windows indeed reveal that detection of the printer is not 100% automatic, and there is a need to "install" the printer (same on linux) from the configuration menu. At least there is no need to use admin privileges, download or execute dependencies, which is sufficient for my use case.

In the interest of TinyUSB as a whole, however, it is interesting to see if that can be improved. I suppose the printer description, which is currently hardcoded here : https://github.com/hathach/tinyusb/pull/3444/files#diff-d649fb44fa8e4a9383e3d84eefb7efd336196be0c8dc66028dd949b45b531437R247 can be adjusted. Switching to a config-defined value is an obvious improvement.

I am also trying to understand what the printer device is supposed to respond to the host on the BULK IN endpoint.