From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <53C550DF.4090500@axelsw.it>
Date: Tue, 15 Jul 2014 18:03:43 +0200
From: Marco Tessore <marco.tessore@axelsw.it>
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Subject: [Xenomai] Question about rtdm_mmap_to user
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To: xenomai@xenomai.org

Good morning,
I would like to share a buffer between user space task and kernel space 
realtime driver.

I used the function rtdm_mmap_to user in the following way:

In the driver, in the function myDriver_ioctl_rt I have the code:

        spild->agg_write_frame_buffer allocated with kalloc

         ret = rtdm_mmap_to_user( user_info,
                 spild->agg_write_frame_buffer,
                 agg_fun_local.data_size,
                 PROT_READ|PROT_WRITE ,
                 &tmpPtr,
                 NULL,
                 NULL
         );
         agg_fun_local.data_buffer = (uint8_t *) tmpPtr;

         rtdm_printk("mmap = %X\n", (unsigned) 
agg_fun_local.data_buffer); // print the returned address

         if (ret)
         {
             rtdm_printk("mmap error1\n");

             kfree(spild->agg_write_frame_buffer);
             return ret;
         }

         // check data
         spild->agg_write_frame_buffer[0] = 0xBE;
         spild->agg_write_frame_buffer[1] = 0xEF;

         // then returned the agg_fun_local structure to userspace

In the user space process I have the following code:
     ret = rt_dev_ioctl( device, IOCTL_MYDRIVER, &agg_fun );
     if (ret)
     {
         printf("PREP_AGG_WRITE failed, ret = %X", (int) ret);
     }

     printf("USER = Address = %X\n", (unsigned) agg_fun.data_buffer);
     printf("USER check %X%X\n", pAggFun->data_buffer[0], 
agg_fun.data_buffer[1]);

I have verified that the address in userspace is the same of the one 
returned by the rtdm_mmap_to_user.
The problem is that in the process I cannot see the check data written 
in the driver.

Is there something wrong in my code?
Are there some constraints tha I haven't took into account?

Thank you very much
Best regards
Marco Tessore