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Date: Sun, 23 Dec 2007 14:09:44 +0100
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From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Subject: Re: [Xenomai-help] RTDM mmap and DMA
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To: Fillod Stephane <stephane.fillod@domain.hid>
Cc: xenomai-help <xenomai@xenomai.org>

Fillod Stephane wrote:
 > Perrine Martignoni wrote:
 > >Currently, I write an RTDM module and I would like to do DMA and mmap
 > to perform transfers who have hard constraints.
 > >I would like to know if there is an example in a driver who would help
 > me to do this.
 > 
 > I'm looking for the same need, except I'm not using RTDM, and everything
 > is in userland. Using the attached patch against Xenomai 2.4.0, I hope
 > to make it to work with something like this:
 > 
 >         RT_HEAP_INFO info;
 >         RT_HEAP heap;
 >         void *user_addr;	/* DMA buffer, user access */
 >         unsigned long dma_addr;	/* for use with the DMA controller */
 > 
 >         /* Allocate memory, suitable for DMA. This occurs before
 > entering RT land. */
 >         err = rt_heap_create (&heap,
 >                         name,
 >                         heapsz,
 >                         H_SHARED|H_DMA);
 >         if (err) { /* ... */ }
 > 
 >         err = rt_heap_alloc (&heap, 0, TM_INFINITE, &user_addr);
 >         if (err) { /* ... */ }
 > 
 >         err = rt_heap_inquire (&heap, &info);
 >         if (err) { /* ... */ }
 > 
 >         dma_addr = info.phys_addr;
 > 
 > Any comments?

You patch looks OK. However, a small detail: can not we use the constant
KMALLOC_MAX_SIZE defined in linux/slab.h instead of defining our own
constant ?

-- 


					    Gilles Chanteperdrix.