| Message ID | 20160901171629.15422-6-andi.shyti@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Sep 02, 2016 at 02:16:27AM +0900, Andi Shyti wrote: > Transmitters do not need to wait until the data has been sent > (and of course received). Return before waiting. > > Signed-off-by: Andi Shyti <andi.shyti@samsung.com> > --- > drivers/media/rc/ir-lirc-codec.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/media/rc/ir-lirc-codec.c b/drivers/media/rc/ir-lirc-codec.c > index c327730..d8953fb 100644 > --- a/drivers/media/rc/ir-lirc-codec.c > +++ b/drivers/media/rc/ir-lirc-codec.c > @@ -153,7 +153,7 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf, > } > > ret = dev->tx_ir(dev, txbuf, count); > - if (ret < 0) > + if (ret < 0 || dev->driver_type == RC_DRIVER_IR_RAW_TX) Just because a driver only does transmit doesn't mean its transmit ABI should change. Now this bit of code is pretty horrible. It ensures that the call to write() takes at least as long as the length of the transmit IR by sleeping. That's not much of a guarantee that the IR has been sent. Note that in the case of ir-spi, since your spi transfer is sync no sleep should be introduced here. The gap calculation in lirc checks that if the call to write() took _longer_ than expected wait before sending the next IR code (when either multiple IR codes or repeats are specified). Introducing the sleep in the kernel here does not help at all, lirc already ensures that it waits as long as the IR is long (see schedule_repeat_timer in lirc). This change was introduced in 3.10, commit f8e00d5. Sean -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi Sean, it's been a while :) I was going through your review fixing what needs to be fixed, but... > > @@ -153,7 +153,7 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf, > > } > > > > ret = dev->tx_ir(dev, txbuf, count); > > - if (ret < 0) > > + if (ret < 0 || dev->driver_type == RC_DRIVER_IR_RAW_TX) > > Just because a driver only does transmit doesn't mean its transmit ABI > should change. > > Now this bit of code is pretty horrible. It ensures that the call to write() > takes at least as long as the length of the transmit IR by sleeping. That's > not much of a guarantee that the IR has been sent. > > Note that in the case of ir-spi, since your spi transfer is sync no sleep > should be introduced here. > > The gap calculation in lirc checks that if the call to write() took _longer_ > than expected wait before sending the next IR code (when either multiple > IR codes or repeats are specified). Introducing the sleep in the kernel > here does not help at all, lirc already ensures that it waits as long as > the IR is long (see schedule_repeat_timer in lirc). > > This change was introduced in 3.10, commit f8e00d5. ... I'm not sure what can be done here. I get your point and I understand that this indeed is a kind of fake sync point and by doing this I How about creating two different functions: - ir_lirc_transmit_ir where we actually do what the function already does - ir_lirc_transmit_no_sync where the function we don't wait because the the sync is done on a different level (for example in the SPI case). SPI does approximately the same thing. Andi -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Oct 27, 2016 at 04:44:01PM +0900, Andi Shyti wrote: > Hi Sean, > > it's been a while :) > > I was going through your review fixing what needs to be fixed, > but... > > > > @@ -153,7 +153,7 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf, > > > } > > > > > > ret = dev->tx_ir(dev, txbuf, count); > > > - if (ret < 0) > > > + if (ret < 0 || dev->driver_type == RC_DRIVER_IR_RAW_TX) > > > > Just because a driver only does transmit doesn't mean its transmit ABI > > should change. > > > > Now this bit of code is pretty horrible. It ensures that the call to write() > > takes at least as long as the length of the transmit IR by sleeping. That's > > not much of a guarantee that the IR has been sent. > > > > Note that in the case of ir-spi, since your spi transfer is sync no sleep > > should be introduced here. > > > > The gap calculation in lirc checks that if the call to write() took _longer_ > > than expected wait before sending the next IR code (when either multiple > > IR codes or repeats are specified). Introducing the sleep in the kernel > > here does not help at all, lirc already ensures that it waits as long as > > the IR is long (see schedule_repeat_timer in lirc). > > > > This change was introduced in 3.10, commit f8e00d5. > > ... I'm not sure what can be done here. I get your point and I > understand that this indeed is a kind of fake sync point and by > doing this I My original plan was to send a patch which just removes the silly wait, but on further investigating debian stable and testing still carry a lirc version that depend on it, so that's not going to fly. > How about creating two different functions: > > - ir_lirc_transmit_ir where we actually do what the function > already does > - ir_lirc_transmit_no_sync where the function we don't wait > because the the sync is done on a different level (for example > in the SPI case). > > SPI does approximately the same thing. Since we have to be able to switch between waiting and not waiting, we need some sort of ABI for this. I think this warrants a new ioctl; I'm not sure how else it can be done. I'll be sending out a patch shortly. Sean -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
October 27, 2016 4:36 PM, "Sean Young" <sean@mess.org> wrote: > Since we have to be able to switch between waiting and not waiting, > we need some sort of ABI for this. I think this warrants a new ioctl; > I'm not sure how else it can be done. I'll be sending out a patch > shortly. Hi Sean, have you considered using a module param for the LIRC bridge module instead? As far as I understand it, this is an issue which is entirely internal to LIRC, and it's also not something which really needs to be changed on a per-device level (either you have a modern LIRC daemon or you don't, and all drivers should behave the same, no?). Another advantage is that the parameter would then go away if and when the lirc bridge ever goes away (yes, I can still dream, can't I?). Regards, David -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hi David, Andi, On Mon, Oct 31, 2016 at 02:31:52PM +0000, David Härdeman wrote: > October 27, 2016 4:36 PM, "Sean Young" <sean@mess.org> wrote: > > Since we have to be able to switch between waiting and not waiting, > > we need some sort of ABI for this. I think this warrants a new ioctl; > > I'm not sure how else it can be done. I'll be sending out a patch > > shortly. > > Hi Sean, > > have you considered using a module param for the LIRC bridge module instead? As far as I understand it, this is an issue which is entirely internal to LIRC, and it's also not something which really needs to be changed on a per-device level (either you have a modern LIRC daemon or you don't, and all drivers should behave the same, no?). I still don't see how any of this would change anything for the ir-spi case: since it uses sync spi transfer, it's going to block anyway. > Another advantage is that the parameter would then go away if and when the lirc bridge ever goes away (yes, I can still dream, can't I?). The suggested ioctl is unique to lirc too and would disappear if the lirc ABI goes away. With a module parameter you would change the lirc ABI into an incompatible one. Not sure that is what module parameters should be used for. Andi, it would be good to know what the use-case for the original change is. Thanks Sean -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/media/rc/ir-lirc-codec.c b/drivers/media/rc/ir-lirc-codec.c index c327730..d8953fb 100644 --- a/drivers/media/rc/ir-lirc-codec.c +++ b/drivers/media/rc/ir-lirc-codec.c @@ -153,7 +153,7 @@ static ssize_t ir_lirc_transmit_ir(struct file *file, const char __user *buf, } ret = dev->tx_ir(dev, txbuf, count); - if (ret < 0) + if (ret < 0 || dev->driver_type == RC_DRIVER_IR_RAW_TX) goto out; for (duration = i = 0; i < ret; i++)
Transmitters do not need to wait until the data has been sent (and of course received). Return before waiting. Signed-off-by: Andi Shyti <andi.shyti@samsung.com> --- drivers/media/rc/ir-lirc-codec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)