Re: [PATCH 01/13] HID: playstation: initial DualSense USB support.

[Roderick Colenbrander <roderick@gaikai.com>]

Hi Barnabás,

Thanks for your review.

On Sun, Dec 27, 2020 at 8:24 AM Barnabás Pőcze <pobrn@protonmail.com> wrote:
>
> Hi
>
>
> 2020. december 19., szombat 7:23 keltezéssel, Roderick Colenbrander írta:
>
> > [...]
> > diff --git a/drivers/hid/hid-playstation.c b/drivers/hid/hid-playstation.c
> > new file mode 100644
> > index 000000000000..8dbd0ae7e082
> > --- /dev/null
> > +++ b/drivers/hid/hid-playstation.c
> > @@ -0,0 +1,317 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later
> > +/*
> > + *  HID driver for Sony DualSense(TM) controller.
> > + *
> > + *  Copyright (c) 2020 Sony Interactive Entertainment
> > + */
> > +
> > +#include <linux/device.h>
> > +#include <linux/hid.h>
> > +#include <linux/input/mt.h>
> > +#include <linux/module.h>
> > +#include <linux/crc32.h>
> > +#include <asm/unaligned.h>
> > +
>
> I believe it would be preferable to keep the list of includes lexicographically
> sorted.
>
>
> > +#include "hid-ids.h"
> > +
> > +/* Base class for playstation devices. */
> > +struct ps_device {
> > +     struct hid_device *hdev;
> > +
> > +     int (*parse_report)(struct ps_device *dev, struct hid_report *report, u8 *data, int size);
> > +};
> > +
> > +#define DS_INPUT_REPORT_USB                  0x01
> > +
> > +/* Button masks for DualSense input report. */
> > +#define DS_BUTTONS0_HAT_SWITCH       GENMASK(3, 0)
> > +#define DS_BUTTONS0_SQUARE   BIT(4)
> > +#define DS_BUTTONS0_CROSS    BIT(5)
> > +#define DS_BUTTONS0_CIRCLE   BIT(6)
> > +#define DS_BUTTONS0_TRIANGLE BIT(7)
> > +#define DS_BUTTONS1_L1               BIT(0)
> > +#define DS_BUTTONS1_R1               BIT(1)
> > +#define DS_BUTTONS1_L2               BIT(2)
> > +#define DS_BUTTONS1_R2               BIT(3)
> > +#define DS_BUTTONS1_CREATE   BIT(4)
> > +#define DS_BUTTONS1_OPTIONS  BIT(5)
> > +#define DS_BUTTONS1_L3               BIT(6)
> > +#define DS_BUTTONS1_R3               BIT(7)
> > +#define DS_BUTTONS2_PS_HOME  BIT(0)
> > +#define DS_BUTTONS2_TOUCHPAD BIT(1)
>
> I believe it would be preferable to explicitly include everything you need
> and not to count on other headers indirectly including it for you. In this
> case `linux/bits.h` is not included.
>
>
> > [...]
> > +/* Common gamepad buttons across DualShock 3 / 4 and DualSense.
> > + * Note: for device with a touchpad, touchpad button is not included
> > + *        as it will be part of the touchpad device.
> > + */
> > +static int ps_gamepad_buttons[] = {
>
> Any reason why it's not `const`?

It should be const.

>
>
> > +     BTN_WEST, /* Square */
> > +     BTN_NORTH, /* Triangle */
> > +     BTN_EAST, /* Circle */
> > +     BTN_SOUTH, /* Cross */
> > +     BTN_TL, /* L1 */
> > +     BTN_TR, /* R1 */
> > +     BTN_TL2, /* L2 */
> > +     BTN_TR2, /* R2 */
> > +     BTN_SELECT, /* Create (PS5) / Share (PS4) */
> > +     BTN_START, /* Option */
> > +     BTN_THUMBL, /* L3 */
> > +     BTN_THUMBR, /* R3 */
> > +     BTN_MODE, /* PS Home */
> > +};
> > [...]
> > +static struct input_dev *ps_allocate_input_dev(struct hid_device *hdev, const char *name_suffix)
> > +{
> > +     struct input_dev *input_dev;
> > +
> > +     input_dev = devm_input_allocate_device(&hdev->dev);
> > +     if (!input_dev)
> > +             return ERR_PTR(-ENOMEM);
> > +
> > +     input_dev->id.bustype = hdev->bus;
> > +     input_dev->id.vendor = hdev->vendor;
> > +     input_dev->id.product = hdev->product;
> > +     input_dev->id.version = hdev->version;
> > +     input_dev->uniq = hdev->uniq;
> > +
> > +     if (name_suffix) {
> > +             input_dev->name = devm_kasprintf(&hdev->dev, GFP_KERNEL, "%s %s", hdev->name,
> > +                             name_suffix);
> > +             if (!input_dev->name)
> > +                     return ERR_PTR(-ENOMEM);
> > +     } else
> > +             input_dev->name = hdev->name;
> > +
>
> As per [1], please use braces around the body of the `else`.
>
>
> > +     input_set_drvdata(input_dev, hdev);
> > +
> > +     return input_dev;
> > +}
> > [...]
> > +static int dualsense_parse_report(struct ps_device *ps_dev, struct hid_report *report,
> > +             u8 *data, int size)
> > +{
> > +     struct hid_device *hdev = ps_dev->hdev;
> > +     struct dualsense *ds = (struct dualsense *)ps_dev;
>
> I believe `container_of(ps_dev, struct dualsense, base)` would be preferable here
> (and everywhere this pattern emerges).

Agreed.

>
> > +     struct dualsense_input_report *ds_report;
> > +     uint8_t value;
> > +
> > +     /* DualSense in USB uses the full HID report for reportID 1, but
> > +      * Bluetooth uses a minimal HID report for reportID 1 and reports
> > +      * the full report using reportID 49.
> > +      */
> > +     if (report->id == DS_INPUT_REPORT_USB && hdev->bus == BUS_USB) {
> > +             ds_report = (struct dualsense_input_report *)&data[1];
> > +     } else {
> > +             hid_err(hdev, "Unhandled reportID=%d\n", report->id);
> > +             return -1;
> > +     }
> > +
> > +     input_report_abs(ds->gamepad, ABS_X, ds_report->x);
> > +     input_report_abs(ds->gamepad, ABS_Y, ds_report->y);
> > +     input_report_abs(ds->gamepad, ABS_RX, ds_report->rx);
> > +     input_report_abs(ds->gamepad, ABS_RY, ds_report->ry);
> > +     input_report_abs(ds->gamepad, ABS_Z, ds_report->z);
> > +     input_report_abs(ds->gamepad, ABS_RZ, ds_report->rz);
> > +
> > +     value = ds_report->buttons[0] & DS_BUTTONS0_HAT_SWITCH;
> > +     if (value > 7)
> > +             value = 8; /* center */
> > +     input_report_abs(ds->gamepad, ABS_HAT0X, ps_gamepad_hat_mapping[value].x);
> > +     input_report_abs(ds->gamepad, ABS_HAT0Y, ps_gamepad_hat_mapping[value].y);
> > +
> > +     input_report_key(ds->gamepad, BTN_WEST, ds_report->buttons[0] & DS_BUTTONS0_SQUARE);
> > +     input_report_key(ds->gamepad, BTN_SOUTH, ds_report->buttons[0] & DS_BUTTONS0_CROSS);
> > +     input_report_key(ds->gamepad, BTN_EAST, ds_report->buttons[0] & DS_BUTTONS0_CIRCLE);
> > +     input_report_key(ds->gamepad, BTN_NORTH, ds_report->buttons[0] & DS_BUTTONS0_TRIANGLE);
> > +     input_report_key(ds->gamepad, BTN_TL, ds_report->buttons[1] & DS_BUTTONS1_L1);
> > +     input_report_key(ds->gamepad, BTN_TR, ds_report->buttons[1] & DS_BUTTONS1_R1);
> > +     input_report_key(ds->gamepad, BTN_TL2, ds_report->buttons[1] & DS_BUTTONS1_L2);
> > +     input_report_key(ds->gamepad, BTN_TR2, ds_report->buttons[1] & DS_BUTTONS1_R2);
> > +     input_report_key(ds->gamepad, BTN_SELECT, ds_report->buttons[1] & DS_BUTTONS1_CREATE);
> > +     input_report_key(ds->gamepad, BTN_START, ds_report->buttons[1] & DS_BUTTONS1_OPTIONS);
> > +     input_report_key(ds->gamepad, BTN_THUMBL, ds_report->buttons[1] & DS_BUTTONS1_L3);
> > +     input_report_key(ds->gamepad, BTN_THUMBR, ds_report->buttons[1] & DS_BUTTONS1_R3);
> > +     input_report_key(ds->gamepad, BTN_MODE, ds_report->buttons[2] & DS_BUTTONS2_PS_HOME);
>
> Possibly this could be replaced with a loop? I have something like this in mind:
>
> ```
> struct ps_gamepad_button {
>   unsigned int code;
>   uint8_t button_idx;
>   uint8_t mask;
> } ps_gamepad_buttons[] = {...};
>
> for (...) {
>   struct ps_gamepad_button *b = ...;
>   input_report_key(...);
> }
> ```
>
> Or is there any reason why the unrolled version is preffered that I'm missing?

It can be done from a loop. Main reason for unrolled was that it is
actually less code and potentially a tiny bit faster, but I bet a
compiler would have unrolled it anyway. I don't know what I want to do
here. Being explicit feels nice (other drivers do something similar).

>
> > +     input_sync(ds->gamepad);
> > +
> > +     return 0;
> > +}
> > +
> > +static struct ps_device *dualsense_create(struct hid_device *hdev)
> > +{
> > +     struct dualsense *ds;
> > +     int ret;
> > +
> > +     ds = devm_kzalloc(&hdev->dev, sizeof(*ds), GFP_KERNEL);
> > +     if (!ds)
> > +             return ERR_PTR(-ENOMEM);
> > +
> > +     /* Patch version to allow userspace to distinguish between
> > +      * hid-generic vs hid-playstation axis and button mapping.
> > +      */
> > +     hdev->version |= 0x8000;
>
> Maybe that '0x8000' could be given a name?

Will do so. Calling it for now 'HID_PLAYSTATION_VERSION_PATCH' or
something like that.

>
>
> > +
> > +     ds->base.hdev = hdev;
> > +     ds->base.parse_report = dualsense_parse_report;
> > +     hid_set_drvdata(hdev, ds);
> > +
> > +     ds->gamepad = ps_gamepad_create(hdev);
> > +     if (IS_ERR(ds->gamepad)) {
> > +             ret = PTR_ERR(ds->gamepad);
> > +             goto err;
> > +     }
> > +
> > +     return (struct ps_device *)ds;
>
> I believe using `&ds->base` instead of `(struct ps_device *)ds` would be somewhat
> better as it does not subvert the type system as much.

Thanks, yeah that's cleaner.

>
>
> > +
> > +err:
> > +     return ERR_PTR(ret);
> > +}
> > +
> > +static int ps_raw_event(struct hid_device *hdev, struct hid_report *report,
> > +             u8 *data, int size)
> > +{
> > +     struct ps_device *dev = hid_get_drvdata(hdev);
> > +
> > +     if (dev && dev->parse_report)
> > +             return dev->parse_report(dev, report, data, size);
> > +
> > +     return 0;
> > +}
> > +
> > +static int ps_probe(struct hid_device *hdev, const struct hid_device_id *id)
> > +{
> > +     struct ps_device *dev;
> > +     int ret;
> > +
> > +     ret = hid_parse(hdev);
> > +     if (ret) {
> > +             hid_err(hdev, "parse failed\n");
> > +             return ret;
> > +     }
> > +
> > +     ret = hid_hw_start(hdev, HID_CONNECT_HIDRAW);
> > +     if (ret) {
> > +             hid_err(hdev, "hw start failed\n");
> > +             return ret;
> > +     }
> > +
> > +     ret = hid_hw_open(hdev);
> > +     if (ret) {
> > +             hid_err(hdev, "hw open failed\n");
> > +             goto err_stop;
> > +     }
> > +
> > +     if (hdev->product == USB_DEVICE_ID_SONY_PS5_CONTROLLER) {
> > +             dev = dualsense_create(hdev);
> > +             if (IS_ERR(dev)) {
> > +                     hid_err(hdev, "Failed to create dualsense.\n");
> > +                     ret = PTR_ERR(dev);
> > +                     goto err_close;
> > +             }
> > +     } else {
>
> When would this be possible?

It isn't possible right now. A colleague really wanted me to add (I
originally didn't have it in an internal build), but I don't mind
taking it out.

>
>
> > +             hid_err(hdev, "Unhandled device\n");
> > +             ret = -EINVAL;
>
> Assuming it's possible, I believe `-ENODEV` is a better error code here.
>
>
> > +             goto err_close;
> > +     }
> > +
> > +     return ret;
> > +
> > +err_close:
> > +     hid_hw_close(hdev);
> > +err_stop:
> > +     hid_hw_stop(hdev);
> > +     return ret;
> > +}
> > [...]
> > +static const struct hid_device_id ps_devices[] = {
> > +     { HID_USB_DEVICE(USB_VENDOR_ID_SONY, USB_DEVICE_ID_SONY_PS5_CONTROLLER),
> > +             .driver_data = 0 },
> > [...]
>
> `.driver_data` would be initialized to zero anyways, why is it necessary to do
> so explicitly?

It is not needed.

>
>
> [1]: https://www.kernel.org/doc/html/latest/process/coding-style.html
>
>
> Regards,
> Barnabás Pőcze

Regards,
Roderick