linux-kernel - Re: [PATCH] vme: fake: fix build for 64-bit dma_addr

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Date:   Thu, 8 Sep 2016 20:10:36 +0100
From:   Martyn Welch <martyn@...chs.me.uk>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Manohar Vanga <manohar.vanga@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] vme: fake: fix build for 64-bit dma_addr_t

On Tue, Sep 06, 2016 at 02:59:41PM +0200, Arnd Bergmann wrote:
> casting between dma_addr_t and a pointer is generally tricky,
> as they might not be the same size and almost never point into
> the same address space. With 32-bit ARM systems and LPAE, we
> get this warning for the vme_fake driver that stores a pointer
> in a dma_addr_t variable:
> 
> drivers/vme/bridges/vme_fake.c: In function 'fake_slave_set':
> drivers/vme/bridges/vme_fake.c:204:29: error: assignment makes pointer from integer without a cast [-Werror=int-conversion]
> 
> To make this clearer while fixing the warning, I'm adding
> a set of helper functions for the type conversion.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Acked-by: Martyn Welch <martyn@...chs.me.uk>

> ---
>  drivers/vme/bridges/vme_fake.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/vme/bridges/vme_fake.c b/drivers/vme/bridges/vme_fake.c
> index 7ef298b289f4..ebf35d305321 100644
> --- a/drivers/vme/bridges/vme_fake.c
> +++ b/drivers/vme/bridges/vme_fake.c
> @@ -48,7 +48,7 @@ struct fake_slave_window {
>  	int enabled;
>  	unsigned long long vme_base;
>  	unsigned long long size;
> -	dma_addr_t buf_base;
> +	void *buf_base;
>  	u32 aspace;
>  	u32 cycle;
>  };
> @@ -114,6 +114,16 @@ static void fake_irq_set(struct vme_bridge *fake_bridge, int level,
>  	/* Nothing to do */
>  }
>  
> +static void *fake_pci_to_ptr(dma_addr_t addr)
> +{
> +	return (void *)(uintptr_t)addr;
> +}
> +
> +static dma_addr_t fake_ptr_to_pci(void *addr)
> +{
> +	return (dma_addr_t)(uintptr_t)addr;
> +}
> +
>  /*
>   * Generate a VME bus interrupt at the requested level & vector. Wait for
>   * interrupt to be acked.
> @@ -202,7 +212,7 @@ static int fake_slave_set(struct vme_slave_resource *image, int enabled,
>  	bridge->slaves[i].enabled = enabled;
>  	bridge->slaves[i].vme_base = vme_base;
>  	bridge->slaves[i].size = size;
> -	bridge->slaves[i].buf_base = buf_base;
> +	bridge->slaves[i].buf_base = fake_pci_to_ptr(buf_base);
>  	bridge->slaves[i].aspace = aspace;
>  	bridge->slaves[i].cycle = cycle;
>  
> @@ -230,7 +240,7 @@ static int fake_slave_get(struct vme_slave_resource *image, int *enabled,
>  	*enabled = bridge->slaves[i].enabled;
>  	*vme_base = bridge->slaves[i].vme_base;
>  	*size = bridge->slaves[i].size;
> -	*buf_base = bridge->slaves[i].buf_base;
> +	*buf_base = fake_ptr_to_pci(bridge->slaves[i].buf_base);
>  	*aspace = bridge->slaves[i].aspace;
>  	*cycle = bridge->slaves[i].cycle;
>  
> @@ -431,7 +441,7 @@ static u8 fake_vmeread8(struct fake_driver *bridge, unsigned long long addr,
>  
>  		if ((addr >= start) && (addr < end)) {
>  			offset = addr - bridge->slaves[i].vme_base;
> -			loc = (u8 *)((void *)bridge->slaves[i].buf_base + offset);
> +			loc = (u8 *)(bridge->slaves[i].buf_base + offset);
>  			retval = *loc;
>  
>  			break;
> @@ -463,7 +473,7 @@ static u16 fake_vmeread16(struct fake_driver *bridge, unsigned long long addr,
>  
>  		if ((addr >= start) && ((addr + 1) < end)) {
>  			offset = addr - bridge->slaves[i].vme_base;
> -			loc = (u16 *)((void *)bridge->slaves[i].buf_base + offset);
> +			loc = (u16 *)(bridge->slaves[i].buf_base + offset);
>  			retval = *loc;
>  
>  			break;
> @@ -495,7 +505,7 @@ static u32 fake_vmeread32(struct fake_driver *bridge, unsigned long long addr,
>  
>  		if ((addr >= start) && ((addr + 3) < end)) {
>  			offset = addr - bridge->slaves[i].vme_base;
> -			loc = (u32 *)((void *)bridge->slaves[i].buf_base + offset);
> +			loc = (u32 *)(bridge->slaves[i].buf_base + offset);
>  			retval = *loc;
>  
>  			break;
> @@ -997,7 +1007,7 @@ static void *fake_alloc_consistent(struct device *parent, size_t size,
>  	void *alloc = kmalloc(size, GFP_KERNEL);
>  
>  	if (alloc != NULL)
> -		*dma = (dma_addr_t)(unsigned long)alloc;
> +		*dma = fake_ptr_to_pci(alloc);
>  
>  	return alloc;
>  }
> @@ -1031,7 +1041,7 @@ static int fake_crcsr_init(struct vme_bridge *fake_bridge)
>  
>  	/* Allocate mem for CR/CSR image */
>  	bridge->crcsr_kernel = kzalloc(VME_CRCSR_BUF_SIZE, GFP_KERNEL);
> -	bridge->crcsr_bus = (dma_addr_t)bridge->crcsr_kernel;
> +	bridge->crcsr_bus = fake_ptr_to_pci(bridge->crcsr_kernel);
>  	if (bridge->crcsr_kernel == NULL)
>  		return -ENOMEM;
>  
> -- 
> 2.9.0
>