On Fri, Jul 01, 2016 at 09:30:35PM +0900, Andi Shyti wrote:
> Hi Sean,
>
> > > The ir-spi is a simple device driver which supports the
> > > connection between an IR LED and the MOSI line of an SPI device.
> > >
> > > The driver, indeed, uses the SPI framework to stream the raw data
> > > provided by userspace through a character device. The chardev is
> > > handled by the LIRC framework and its functionality basically
> > > provides:
> > >
> > > - raw write: data to be sent to the SPI and then streamed to the
> > > MOSI line;
> > > - set frequency: sets the frequency whith which the data should
> > > be sent;
> > > - set length: sets the data length. This information is
> > > optional, if the length is set, then userspace should send raw
> > > data only with that length; while if the length is set to '0',
> > > then the driver will figure out himself the length of the data
> > > based on the length of the data written on the character
> > > device.
> > > The latter is not recommended, though, as the driver, at
> > > any write, allocates and deallocates a buffer where the data
> > > from userspace are stored.
> > >
> > > The driver provides three feedback commands:
> > >
> > > - get length: reads the length set and (as mentioned), if the
> > > length is '0' it will be calculated at any write
> > > - get frequency: the driver reports the frequency. If userpace
> > > doesn't set the frequency, the driver will use a default value
> > > of 38000Hz.
> >
> > This interface is not compatible with other lirc devices; there is no
> > way of determining whether this is a regular lirc device or this new
> > flavour you've invented.
>
> except of the set length and get length which I'm using a bit
> freely because I am dealing with devices that exchange always the
> same amount of data, so that I don't need (in my case) to
> pre-allocate or overallocate or runtime allocate. I don't
> understand what else I invented :)
Other than the LIRC_{GET,SET}_LENGTH it might very well be compatible;
you're reusing LIRC_GET_LENGTH for a different purpose.
Is the kmalloc() really that costly that it needs to be avoided for
each transmit?
> This is a simple driver which is driving an LED connected through
> SPI and userspace writes raw data in it (LIRC_CAN_SEND_RAW).
And some odd ioctl.
> > Also I don't see what justifies this new interface. This can be
> > implemented in rc-core in less lines of code and it will be entirely
> > compatible with existing user-space.
>
> Also here I'm getting a bit confused. When I started writing
> this, I didn't even know of the existence of a remote controlling
> framework, but then I run across this:
>
> "LIRC is a package that allows you to decode and send infra-red
> signals of many (but not all) commonly used remote controls. "
>
> taken from lirc.org: my case is exactly falling into this
> description.
>
> Am I missing anything?
See drivers/staging/media/lirc/TODO: "All drivers should either be
ported to ir-core, or dropped entirely". ir-core has since been renamed
to rc-core; it is uses for non-IR purposes like cec.
lirc exists as the user-space ABI but not it is not the preferred
framework for kernel space.
There is one problem here. rc-core does not provide very well for
transmit-only hardware, so rc-core needs some modifications. This is
what I suggest to make it work:
1. in include/media/rc-core.h add a new entry to the enum rc_driver_type
called "RC_DRIVER_IR_RAW_TX_ONLY" (or something like that).
2. rc_allocate_device() needs an argument "enum rc_driver_type"; in the
case it would not allocate an input device. All drivers needs to
pass in this argument.
3. rc_register_device() and rc_unregister_device() should not execute
anything with to do with input devices or key maps for tx only
devices.
4. ir_lirc_register() should not set the LIRC_CAN_REC_MODE2 feature
or allocate an input buffer in the case of TX only device.
With these changes all you need to do in ir-spi is:
struct rc_dev *rc = rc_allocate_device(RC_DRIVER_IR_RAW_TX_ONLY);
strcpy(rc->name, "IR SPI");
rc->s_tx_carrier = ir_spi_set_tx_carrier; // write function
rc->tx_ir = ir_spi_tx; // write function
rc->driver_name = "ir-spi";
rc_register_driver(rc);
I'm happy to help.
Sean
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