Hello.
On 24-04-2013 10:53, Lee Jones wrote:
struct musb_hdrc_platform_data *plat = dev->platform_data;
- struct ux500_musb_board_data *data = plat->board_data;
+ struct ux500_musb_board_data *data;
- param_array = data->dma_rx_param_array;
+ param_array = (data) ? data->dma_rx_param_array : NULL;
Why enclose a simple variable in parens?
Because 'data' is a pointer, so it contains a memory location,
Pointer points to memory location, not contains it.
but if
'plat->board_data' is NULL, then 'data' will be NULL (essentially
memory location 0x00000000).
So what?
So if we were to read-in to 'struct ux500_musb_board_data *data', by
index 'dma_rx_param_array', which I believe is '0' in this case:
struct ux500_musb_board_data {
void **dma_rx_param_array;
void **dma_tx_param_array;
bool (*dma_filter)(struct dma_chan *chan, void *filter_param);
};
... then we're saying take the data from this memory location:
param_array = *((0x00000000)->(0x0));
Which will cause a kernel Oops, due to the fact that address 0x0 isn't
allocated to us, so you get something like:
"Unable to handle kernel NULL pointer dereference at virtual address 00000000"
We're not dereferencing 'data', so I completely fail to follow you.
Hope that helps.
Not at all.
Kind regards,
Lee
WBR, Sergei
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