SOC: Zedboard: Driver question

[priyaranjan]

On Thu, Jun 12, 2014 at 7:09 PM, amit mehta <gmate.amit at gmail.com> wrote:

> We are working on a school project in which we are trying to develop a
> audio mixer
> on Zedboard (Development board from Digilent). We have developed the IP
> and have
> integrated it with the overall hardware using Programmable logic. This
> board has ARM
> core. We have a Digilent pre-configured Linux source which we
> cross-compiled
> for ARM board, device tree blob and bootloader for Zync(BOOT.BIN). The
> system
> boots fine with Linux, but now to expose the recently added hardware
> implementation
> of audio mixer, we are trying to develop the driver using the platform
> driver API.
> Currently, In our reconfigurable hardware, we have 2 channels and a mixer
> and we
> want to access those individually as some file nodes under /proc FS. The
> sample
> code is shown below:
>
> <snip from myiir.c>
> /* device match table to match with device node in device tree
>  * These are the list of devices that we want to expose as platform device
>  */
> static const struct of_device_id myiir_of_match[] __devinitconst = {
>         {.compatible = "dglnt,myiir-audio-ch0"},
>         {.compatible = "dglnt,myiir-audio-ch1"},
>         {.compatible = "dglnt,myiir-audio-mix0"},
>         {},
> };
>
> MODULE_DEVICE_TABLE(of, myiir_of_match);
>
> /* platform driver structure for myiir driver */
> static struct platform_driver myiir_driver = {
>         .driver = {
>                 .name = DRIVER_NAME,
>                 .owner = THIS_MODULE,
>                 .of_match_table = myiir_of_match},
>         .probe = myiir_probe,
>         .remove = __devexit_p(myiir_remove),
>         .shutdown = __devexit_p(myiir_shutdown)
> };
>
> /* Register myiir platform driver */
> module_platform_driver(myiir_driver);
> <myiir.c>
>
> Now, inside the probe routine (myiir_probe), can we create proc
> entries by calling
> create_proc for each of these nodes and setting the appropriate read and
> write
> methods(file_operations) ?
>


Yes, I feel this is fine, the proc entries to be created in probe,
 Initialize all data structures as required in probe.



>
> <snip from the myiir_probe>
> struct proc_dir_entry *myiir_proc_entry[3];
>
> myiir_proc_entry[0] = proc_create("myiir-audio-ch0", 0, NULL,
>                 &proc_myiir_ch0_operations);
>
> myiir_proc_entry[1] = proc_create("myiir-audio-ch1", 0, NULL,
>                 &proc_myiir_ch1_operations);
>
> myiir_proc_entry[2] = proc_create("myiir-audio-mix0", 0, NULL,
>                 &proc_myiir_mix0_operations);
>
> <snip from the myiir_probe>
>
> While browsing the Internet, we found some sample driver code, which we are
> also using as a template. I've attached the driver that is based on
> the same template.
>
> <snip from device tree file>
> myiir-aud-ch0 {
>             compatible = "dglnt,myiir-audio-ch0";
>             reg = <0x74200000 0x10000>;
>         };
>         myiir-aud-ch1 {
>             compatible = "dglnt,myiir-audio-ch1";
>             reg = <0x74220000 0x10000>;
>         };
>         myiir-aud-mix0 {
>             compatible = "dglnt,myiir-audio-mix0";
>             reg = <0x68600000 0x10000>;
>         };
> <snip from device tree file>
>
> The driver is far from complete, but as of now the compilation woks fine.
> <snip>
> user at fpga4v:~/tutorial/IIRdriver$ make ARCH=arm
> CROSS_COMPILE=arm-xilinx-linux-gnueabi-
> make -C ../linux-digilent-3.6-digilent-13.01/
> M=/home/user/tutorial/IIRdriver modules
> make[1]: Entering directory
> `/home/user/tutorial/linux-digilent-3.6-digilent-13.01'
>   CC [M]  /home/user/tutorial/IIRdriver/myiir.o
>   Building modules, stage 2.
>   MODPOST 1 modules
>   CC      /home/user/tutorial/IIRdriver/myiir.mod.o
>   LD [M]  /home/user/tutorial/IIRdriver/myiir.ko
> make[1]: Leaving directory
> `/home/user/tutorial/linux-digilent-3.6-digilent-13.01'
> <snip>
>
>
Overall this looks to be a good attempt .Kumar :)


> Thanks,
> Kumar
>
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