From e70d13f7ac061da3fcb982a049e98f63b7ded3d9 Mon Sep 17 00:00:00 2001 From: Sean Young Date: Fri, 9 Aug 2019 18:47:41 -0300 Subject: [PATCH] media: imon_raw: simplify and explain bit operations This code needs some explanation. Signed-off-by: Sean Young Signed-off-by: Mauro Carvalho Chehab --- drivers/media/rc/imon_raw.c | 43 ++++++++++++++++++++++++++++++++++--------- 1 file changed, 34 insertions(+), 9 deletions(-) diff --git a/drivers/media/rc/imon_raw.c b/drivers/media/rc/imon_raw.c index 25e56c5b13c0..e6723993b466 100644 --- a/drivers/media/rc/imon_raw.c +++ b/drivers/media/rc/imon_raw.c @@ -14,7 +14,7 @@ struct imon { struct device *dev; struct urb *ir_urb; struct rc_dev *rcdev; - u8 ir_buf[8] __aligned(__alignof__(u64)); + __be64 ir_buf; char phys[64]; }; @@ -29,14 +29,35 @@ struct imon { static void imon_ir_data(struct imon *imon) { struct ir_raw_event rawir = {}; - u64 d = be64_to_cpup((__be64 *)imon->ir_buf) >> 24; + u64 data = be64_to_cpu(imon->ir_buf); + u8 packet_no = data & 0xff; int offset = 40; int bit; - dev_dbg(imon->dev, "data: %*ph", 8, imon->ir_buf); + if (packet_no == 0xff) + return; + + dev_dbg(imon->dev, "data: %*ph", 8, &imon->ir_buf); + + /* + * Only the first 5 bytes contain IR data. Right shift so we move + * the IR bits to the lower 40 bits. + */ + data >>= 24; do { - bit = fls64(d & (BIT_ULL(offset) - 1)); + /* + * Find highest set bit which is less or equal to offset + * + * offset is the bit above (base 0) where we start looking. + * + * data & (BIT_ULL(offset) - 1) masks off any unwanted bits, + * so we have just bits less than offset. + * + * fls will tell us the highest bit set plus 1 (or 0 if no + * bits are set). + */ + bit = fls64(data & (BIT_ULL(offset) - 1)); if (bit < offset) { dev_dbg(imon->dev, "pulse: %d bits", offset - bit); rawir.pulse = true; @@ -49,7 +70,12 @@ static void imon_ir_data(struct imon *imon) offset = bit; } - bit = fls64(~d & (BIT_ULL(offset) - 1)); + /* + * Find highest clear bit which is less than offset. + * + * Just invert the data and use same trick as above. + */ + bit = fls64(~data & (BIT_ULL(offset) - 1)); dev_dbg(imon->dev, "space: %d bits", offset - bit); rawir.pulse = false; @@ -59,7 +85,7 @@ static void imon_ir_data(struct imon *imon) offset = bit; } while (offset > 0); - if (imon->ir_buf[7] == 0x0a) { + if (packet_no == 0x0a) { ir_raw_event_set_idle(imon->rcdev, true); ir_raw_event_handle(imon->rcdev); } @@ -72,8 +98,7 @@ static void imon_ir_rx(struct urb *urb) switch (urb->status) { case 0: - if (imon->ir_buf[7] != 0xff) - imon_ir_data(imon); + imon_ir_data(imon); break; case -ECONNRESET: case -ENOENT: @@ -129,7 +154,7 @@ static int imon_probe(struct usb_interface *intf, imon->dev = &intf->dev; usb_fill_int_urb(imon->ir_urb, udev, usb_rcvintpipe(udev, ir_ep->bEndpointAddress), - imon->ir_buf, sizeof(imon->ir_buf), + &imon->ir_buf, sizeof(imon->ir_buf), imon_ir_rx, imon, ir_ep->bInterval); rcdev = devm_rc_allocate_device(&intf->dev, RC_DRIVER_IR_RAW); -- 2.11.0