trem wrote: > Hi > > Here is the second part of the tutorial serie about rtdm. I've just > added rt-task and semaphore. It's still a very very simple example.
Thanks again for your contribution. I have a few comments below.
>
> Now, I don't know how to continue, have you got any idea of
> "topic/subject" that could help people to understand xenomai ?
I think it would be good to dive into IRQ handling as this is part of
most drivers. Have a look at irqbench, specifically the UART part of it,
and the 16550A serial driver. Maybe you can try to create some topics
around a basic null-modem link between a Xenomai box and some other PC.
That would give you an IRQ source, a data source (the transmitted
characters), and enough food for things like synchronisation (mutexes,
spinlocks). Don't reimplement the full 16550A driver, only pick simple
aspects.
>
> regards,
> Philippe
>
>
> ------------------------------------------------------------------------
>
...
> Index: tut02-skeleton-drv.c
> ===================================================================
> --- tut02-skeleton-drv.c (révision 0)
> +++ tut02-skeleton-drv.c (révision 0)
> @@ -0,0 +1,245 @@
> +/***************************************************************************
> + * Copyright (C) 2007 by trem (Philippe Reynes) *
> + * [EMAIL PROTECTED] *
> + * *
> + * This program is free software; you can redistribute it and/or modify *
> + * it under the terms of the GNU General Public License as published by *
> + * the Free Software Foundation; either version 2 of the License, or *
> + * (at your option) any later version. *
> + * *
> + * This program is distributed in the hope that it will be useful, *
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of *
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
> + * GNU General Public License for more details. *
> + * *
> + * You should have received a copy of the GNU General Public License *
> + * along with this program; if not, write to the *
> + * Free Software Foundation, Inc., *
> + * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *
> + ***************************************************************************/
> +
> +/**
> + * This kernel driver demonstrates how an RTDM device can be set up.
This sounds familiar, like the first example. Doesn't this emphasis a
new, different topic?
> + *
> + * It is a simple device, only 4 operation are provided:
> + * - open: start device usage
> + * - close: ends device usage
> + * - write: store transfered data in an internal buffer (realtime context)
> + * - read: return previously stored data and erase buffer (realtime
> context)
> + *
> + */
> +
> +#include <linux/module.h>
> +#include <rtdm/rtdm_driver.h>
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("trem");
> +
> +#define SIZE_MAX 1024
> +#define DEVICE_NAME "tut02-skeleton-drv01"
> +#define SOME_SUB_CLASS 4711
> +
> +/**
> + * The structure of the buffer
> + *
> + */
> +typedef struct buffer_s {
> + int size;
> + char data[SIZE_MAX];
> +} buffer_t;
> +
> +/**
> + * The global buffer
> + *
> + */
> +buffer_t buffer;
> +
> +/**
> + * The global semaphore
> + *
> + */
> +rtdm_sem_t sem;
Having plain global variables doesn't scale well. That actually makes me
think of further topcis for tutorials:
o Handling multiple devices with one driver
o Making use of device context buffers (rtdm_device::context_size)
> +
> +/**
> + * Open the device
> + *
> + * This function is called when the device shall be opened.
> + *
> + */
> +static int simple_rtdm_open_nrt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info, int oflags)
> +{
> + return 0;
> +}
> +
> +/**
> + * Open the device
> + *
> + * This function is called when the device shall be opened in
> realtime-context.
> + *
> + */
> +static int simple_rtdm_open_rt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info, int oflags)
> +{
> + return 0;
> +}
Don't register separate handlers for the same operation if they are
identical.
> +
> +/**
> + * Close the device
> + *
> + * This function is called when the device shall be closed.
> + *
> + */
> +static int simple_rtdm_close_nrt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info)
> +{
> + return 0;
> +}
> +
> +/**
> + * Close the device
> + *
> + * This function is called when the device shall be closed in
> realtime-context.
> + *
> + */
> +static int simple_rtdm_close_rt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info)
> +{
> + return 0;
> +}
Same here.
> +
> +/**
> + * Read from the device
> + *
> + * This function is called when the device is read in non-realtime context.
> + *
> + */
> +static ssize_t simple_rtdm_read_nrt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info, void *buf,
> + size_t nbyte)
> +{
> + rtdm_printk("DEBUG : read is not implemented in non-realtime
> context\n");
> + return 0;
Don't do this. If there is no nrt handler registered, Xenomai will
nicely switch a shadowed caller into RT mode (when required) and call
simple_rtdm_read_rt instead. With this handler registered, nothing
useful happens. Rather demonstrate context-sensitive handlers by doing
different things with them (but that's advanced stuff anyway).
> +}
> +
> +/**
> + * Read from the device
> + *
> + * This function is called when the device is read in realtime context.
> + *
> + */
> +static ssize_t simple_rtdm_read_rt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info, void *buf,
> + size_t nbyte)
> +{
> + int size;
> +
> + /* take the semaphore */
> + rtdm_sem_down(&sem);
> +
> + /* read the kernel buffer and sent it to user space */
> + size = (buffer.size > nbyte) ? nbyte : buffer.size;
> + if (rtdm_safe_copy_to_user(user_info, buf, buffer.data, size))
> + rtdm_printk("ERROR : can't copy data from driver\n");
Send the error code to the user instead of dumping it to the log. The
user will then be able to react on it.
> +
> + /* clean the kernel buffer */
> + buffer.size = 0;
> +
> + return size;
> +}
> +
> +/**
> + * Write in the device
> + *
> + * This function is called when the device is written in non-realtime
> context.
> + *
> + */
> +static ssize_t simple_rtdm_write_nrt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info,
> + const void *buf, size_t nbyte)
> +{
> + rtdm_printk("DEBUG : write is not implemented in non-realtime
> context\n");
> + return 0;
> +}
See above.
> +
> +/**
> + * Write in the device
> + *
> + * This function is called when the device is written in realtime context.
> + *
> + */
> +static ssize_t simple_rtdm_write_rt(struct rtdm_dev_context *context,
> + rtdm_user_info_t * user_info,
> + const void *buf, size_t nbyte)
> +{
> + /* release the semaphore */
> + rtdm_sem_up(&sem);
Oops, that creates a race: Data will be written to the buffer AFTER you
signal some reader that there is data available...
> +
> + /* write the user buffer in the kernel buffer */
> + buffer.size = (nbyte > SIZE_MAX) ? SIZE_MAX : nbyte;
> + if (rtdm_safe_copy_from_user(user_info, buffer.data, buf, buffer.size))
> + rtdm_printk("ERROR : can't copy data to driver\n");
> +
> + return nbyte;
> +}
> +
> +/**
> + * This structure describe the simple RTDM device
> + *
> + */
> +static struct rtdm_device device = {
> + .struct_version = RTDM_DEVICE_STRUCT_VER,
> +
> + .device_flags = RTDM_NAMED_DEVICE,
> + .context_size = 0,
> + .device_name = DEVICE_NAME,
> +
> + .open_nrt = simple_rtdm_open_nrt,
> + .open_rt = simple_rtdm_open_rt,
> +
> + .ops = {
> + .close_nrt = simple_rtdm_close_nrt,
> + .close_rt = simple_rtdm_close_rt,
> + .read_nrt = simple_rtdm_read_nrt,
> + .read_rt = simple_rtdm_read_rt,
> + .write_nrt = simple_rtdm_write_nrt,
> + .write_rt = simple_rtdm_write_rt,
> + },
> +
> + .device_class = RTDM_CLASS_EXPERIMENTAL,
> + .device_sub_class = SOME_SUB_CLASS,
> + .profile_version = 1,
> + .driver_name = "SimpleRTDM",
> + .driver_version = RTDM_DRIVER_VER(0, 1, 2),
> + .peripheral_name = "Simple RTDM example",
> + .provider_name = "trem",
> + .proc_name = device.device_name,
> +};
> +
> +/**
> + * This function is called when the module is loaded
> + *
> + * It simply registers the RTDM device.
> + *
> + */
> +int __init simple_rtdm_init(void)
> +{
> + buffer.size = 0; /* clear the buffer */
> + rtdm_sem_init(&sem, 0); /* init the global semaphore */
> +
> + return rtdm_dev_register(&device);
> +}
> +
> +/**
> + * This function is called when the module is unloaded
> + *
> + * It unregister the RTDM device, polling at 1000 ms for pending users.
> + *
> + */
> +void __exit simple_rtdm_exit(void)
> +{
> + rtdm_dev_unregister(&device, 1000);
> +}
> +
> +module_init(simple_rtdm_init);
> +module_exit(simple_rtdm_exit);
>
> Modification de propriétés sur tut02-skeleton-drv.c
> ___________________________________________________________________
> Nom : svn:eol-style
> + native
>
> Index: Makefile
> ===================================================================
> --- Makefile (révision 2484)
> +++ Makefile (copie de travail)
> @@ -1,13 +1,13 @@
> ###### CONFIGURATION ######
>
> ### List of applications to be build
> -APPLICATIONS = tut01-skeleton-app
> +APPLICATIONS = tut01-skeleton-app tut02-skeleton-app
>
> ### Note: to override the search path for the xeno-config script, use "make
> XENO=..."
>
>
> ### List of modules to be build
> -MODULES = heartbeat-x86 tut01-skeleton-drv
> +MODULES = heartbeat-x86 tut01-skeleton-drv tut02-skeleton-drv
>
> ### Note: to override the kernel source path, use "make KSRC=..."
>
> @@ -86,6 +86,6 @@
>
> clean::
> $(RM) $(CLEANMOD) *.o *.ko *.mod.c Module*.symvers
> - $(RM) -R .tmp*
> + $(RM) -R *~ .tmp*
This last hunk looks unrelated.
Jan
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