Le sam. 7 juil. 2018 à 9:34, PrasannaKumar Muralidharan
<prasannatsmkumar@xxxxxxxxx> a écrit :
On 5 July 2018 at 23:56, Paul Cercueil <paul@xxxxxxxxxxxxxxx> wrote:
Hi PrasannaKumar,
Hi Paul,
On 3 July 2018 at 18:02, Paul Cercueil <paul@xxxxxxxxxxxxxxx>
wrote:
As part of the work to support various other Ingenic JZ47xx SoC
versions,
which don't feature the same number of DMA channels per core, we
now
deduce the number of DMA channels available from the devicetree
compatible string.
Signed-off-by: Paul Cercueil <paul@xxxxxxxxxxxxxxx>
---
drivers/dma/dma-jz4780.c | 53
+++++++++++++++++++++++++++++-----------
1 file changed, 39 insertions(+), 14 deletions(-)
diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
index 85820a2d69d4..b40f491f0367 100644
--- a/drivers/dma/dma-jz4780.c
+++ b/drivers/dma/dma-jz4780.c
@@ -16,6 +16,7 @@
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/of.h>
+#include <linux/of_device.h>
#include <linux/of_dma.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
@@ -23,8 +24,6 @@
#include "dmaengine.h"
#include "virt-dma.h"
-#define JZ_DMA_NR_CHANNELS 32
-
/* Global registers. */
#define JZ_DMA_REG_DMAC 0x1000
#define JZ_DMA_REG_DIRQP 0x1004
@@ -135,14 +134,20 @@ struct jz4780_dma_chan {
unsigned int curr_hwdesc;
};
+enum jz_version {
+ ID_JZ4780,
+};
+
struct jz4780_dma_dev {
struct dma_device dma_device;
void __iomem *base;
struct clk *clk;
unsigned int irq;
+ unsigned int nb_channels;
+ enum jz_version version;
uint32_t chan_reserved;
- struct jz4780_dma_chan chan[JZ_DMA_NR_CHANNELS];
+ struct jz4780_dma_chan chan[];
Looks like a variable length array in struct. I think there is some
effort to remove the usage of VLA. Can you revisit this? I may be
wrong, please feel free to correct.
Are you sure? It's the first time I hear about it.
Could anybody confirm?
Please see [1] for info.
Variable Length Arrays in struct is expressly forbidden in C99, C11.
Clang does not support it. To make kernel compile with Clang few
people are trying to remove/reduce VLAIS usage.
1.
https://blog.linuxplumbersconf.org/2013/ocw/system/presentations/1221/original/VLAIS.pdf
I read it, and my structure is not a VLAIS; my "chan" array is a
flexible
array, its sizeof() is 0, so the sizeof() of the structure is constant.
See page 6 of the PDF, about alternatives to VLAIS:
"If possible use a flexible array member and move the array to the end
of
the struct"
Which is what I am doing here.
-Paul
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