[PATCH 1/2] netcp: try to reduce type confusion in descriptors

[David Miller]

From: Arnd Bergmann <arnd at arndb.de>
Date: Tue, 08 Dec 2015 16:32:27 +0100

> The netcp driver produces tons of warnings when CONFIG_LPAE is enabled
> on ARM:
> 
> drivers/net/ethernet/ti/netcp_core.c: In function 'netcp_tx_map_skb':
> drivers/net/ethernet/ti/netcp_core.c:1084:13: warning: passing argument 1 of 'set_words' from incompatible pointer type [-Wincompatible-pointer-types]
> 
> This is the result of trying to pass a pointer to a dma_addr_t to
> a function that expects a u32 pointer to copy that into a DMA descriptor.
> 
> Looking at that code in more detail to fix the warnings, I see multiple
> related problems:
> 
> * The conversion functions are not endian-safe, as the DMA descriptors
>   are almost certainly fixed-endian, but the CPU is not.
> 
> * On 64-bit machines, passing a pointer through a u32 variable is a
>   bug, accessing an indirect pointer as a u32 pointer even more so.
> 
> * The handling of epib and psdata mixes native-endian and device-endian
>   data.
> 
> In this patch, I try to sort out the types for most accesses here,
> adding le32_to_cpu/cpu_to_le32 where appropriate, and passing pointers
> through two 32-bit words in the descriptor padding, to make it plausible
> that the driver does the right thing if compiled for big-endian or
> 64-bit systems.
> 
> Signed-off-by: Arnd Bergmann <arnd at arndb.de>

Applied to net-next.