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

From: "Barnabás Pőcze" <pobrn@protonmail.com>
To: Roderick Colenbrander <roderick@gaikai.com>
Cc: Jiri Kosina <jikos@kernel.org>,
	Benjamin Tissoires <benjamin.tissoires@redhat.com>,
	"linux-input@vger.kernel.org" <linux-input@vger.kernel.org>,
	Chris Ye <lzye@google.com>,
	Roderick Colenbrander <roderick.colenbrander@sony.com>
Subject: Re: [PATCH 01/13] HID: playstation: initial DualSense USB support.
Date: Tue, 29 Dec 2020 19:12:49 +0000	[thread overview]
Message-ID: <8rsKxzY-iTczahhdGPIJKVLelQDsVzynWy9njvI9ZaOE-1qQbbE3yXMhLztiPzkkgvMPSwwb_B_rDX-YYKxir9lXR1h1CyPAIdtGABmzaco=@protonmail.com> (raw)
In-Reply-To: <CANndSKkV5HNtR=CkDekmt8xeNjSdS0Kvws5d0MQcdHV1Bf8diw@mail.gmail.com>

2020. december 28., hétfő 0:04 keltezéssel, Roderick Colenbrander írta:

> [...]
> > > +     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).
> [...]

I agree that the compiler would've probably unrolled it. I'd personally consider
the loop version to be shorter as I'd not consider the static array "code" -
it's really just data initialization. Anyways, may I suggest then to align the
parameters so that the given parameter of each call starts in the same column?
I think it helps readability a good deal.