FreeCalypso > hg > freecalypso-hwlab
comparison linux-patch/README @ 83:d7a1e7a6d6ba
linux-patch: current best offering of minpatch-*
| author | Mychaela Falconia <falcon@freecalypso.org> |
|---|---|
| date | Sun, 06 Dec 2020 02:55:40 +0000 |
| parents | |
| children | 95c2a67e1219 |
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| 82:e2161ac7d641 | 83:d7a1e7a6d6ba |
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| 1 This directory contains several versions of the Linux kernel ftdi_sio driver | |
| 2 patch that adds support for FreeCalypso DUART28C adapter, i.e., the optional | |
| 3 configuration of DUART28 with boot control outputs. | |
| 4 | |
| 5 The version in the orig-202007 directory was produced at the end of 2020-07, | |
| 6 when DUART28 hardware was still being designed; this original version of the | |
| 7 patch was created to test the idea and to prove it working (using a generic | |
| 8 FT2232D board and an oscilloscope), and it was created with the mindset of a | |
| 9 hardware engineer, rather than that of Linux kernel maintainers. This original | |
| 10 patch version was made against kernel version 4.4.14 (the version used by the | |
| 11 Mother), and it predates all later mainline submission and integration attempts. | |
| 12 | |
| 13 A patch series against then-current mainline was submitted to ftdi_sio driver | |
| 14 maintainer Johan Hovold in 2020-09 for inclusion in mainline Linux. The | |
| 15 preliminary patch adding support for FreeCalypso JTAG+UART USB ID codes was | |
| 16 readily accepted and has since been propagated to several stable kernel branches | |
| 17 (4.4.240, 4.9.240, 4.14.202, 4.19.152, 5.4.72, 5.8.16, 5.9.1 and mainline 5.10), | |
| 18 but this patch by itself does not help in any way with DUART28C support. The | |
| 19 remaining two patches from the original 2020-09 patch series (a preliminary | |
| 20 patch fixing an oversight in the quirk interface and then the main patch of | |
| 21 interest) were met with resistance, however, and the goal of bringing DUART28C | |
| 22 support into mainline Linux is still in limbo as of 2020-12. | |
| 23 | |
| 24 Johan (the ftdi_sio driver maintainer who was the target of our initial pressure | |
| 25 campaign to get the needed driver quirk accepted) has now proposed a generalized | |
| 26 version of Mother Mychaela's original idea; this generalized version is just as | |
| 27 good for our purposes because in the end it still recognizes our custom USB ID | |
| 28 and sets the quirk flag which we require, but it also helps other potential | |
| 29 users who may have similar needs, but who work with "any" serial port rather | |
| 30 than a custom USB ID. The current version as of this writing of Johan's patch | |
| 31 series implementing his proposed generalized solution is this one: | |
| 32 | |
| 33 https://lore.kernel.org/linux-serial/X8iuCXYhOBVMGvXv@localhost/T/ | |
| 34 | |
| 35 However, the comments in that thread indicate that the maintainers seem intent | |
| 36 on delaying this integration until 5.12 merge window if not even later, thus we | |
| 37 are still months away from any hope of resolution. Because We The End Users | |
| 38 cannot be expected to put our lives on hold and just sit and wait for kernel | |
| 39 maintainers to get their act together, we need some immediate solution for our | |
| 40 use right now - and the minpatch-* series presented here is our current best | |
| 41 offering for end user purposes. | |
| 42 | |
| 43 3 end user patch series versions are presented in minpatch-4.4.14, | |
| 44 minpatch-4.4.240 and minpatch-4.9.240. 4.4.240 and 4.9.240 already include the | |
| 45 preliminary JTAG+UART USB ID code support patch (which serves mainly as an | |
| 46 anchor marking the place where the new DUART28C USB ID code needs to go in | |
| 47 ftdi_sio_ids.h and in the ftdi_sio.c ID code table), but 4.4.14 predates this | |
| 48 patch by a few years, thus minpatch-4.4.14 includes a backport of this | |
| 49 preliminary patch as well. After this preliminary patch, each minpatch-* | |
| 50 version includes the quirk port_probe patch and the main patch adding DUART28C | |
| 51 support with the needed quirk. These latter patches are the closest version we | |
| 52 have to what we are hoping to see eventually merged into mainline, and they have | |
| 53 already undergone rounds of revision in response to maintainer Johan's criticism | |
| 54 - but this "minimal patch" version is limited to just the ftdi_sio driver, not | |
| 55 extending into more generic layers, hence the actual quirk flag is implemented | |
| 56 inside ftdi_sio, not fully generalized like it is in the version which we are | |
| 57 hoping to see merged into mainline in future months/years. |