Re: [Qemu-devel] [PATCH 03/14] sdhci: use the ldst_le_dma() API

[Philippe Mathieu-Daudé]

On Thu, Dec 14, 2017 at 2:23 PM, Alistair Francis
<address@hidden> wrote:
> On Wed, Dec 13, 2017 at 11:58 AM, Philippe Mathieu-Daudé
> <address@hidden> wrote:
>> This makes the code slightly safer, also easier to review.
>>
>> Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
>> ---
>>  hw/sd/sdhci.c | 23 +++++++----------------
>>  1 file changed, 7 insertions(+), 16 deletions(-)
>>
>> diff --git a/hw/sd/sdhci.c b/hw/sd/sdhci.c
>> index 312b167bfa..e39623baba 100644
>> --- a/hw/sd/sdhci.c
>> +++ b/hw/sd/sdhci.c
>> @@ -603,14 +603,12 @@ typedef struct ADMADescr {
>>
>>  static void get_adma_description(SDHCIState *s, ADMADescr *dscr)
>>  {
>> -    uint32_t adma1 = 0;
>> -    uint64_t adma2 = 0;
>> +    uint32_t adma1;
>> +    uint64_t adma2;
>>      hwaddr entry_addr = (hwaddr)s->admasysaddr;
>>      switch (SDHC_DMA_TYPE(s->hostctl)) {
>>      case SDHC_CTRL_ADMA2_32:
>> -        dma_memory_read(&address_space_memory, entry_addr, (uint8_t 
>> *)&adma2,
>> -                        sizeof(adma2));
>> -        adma2 = le64_to_cpu(adma2);
>> +        adma2 = ldq_le_dma(&address_space_memory, entry_addr);
>>          /* The spec does not specify endianness of descriptor table.
>>           * We currently assume that it is LE.
>>           */
>> @@ -620,9 +618,7 @@ static void get_adma_description(SDHCIState *s, 
>> ADMADescr *dscr)
>>          dscr->incr = 8;
>>          break;
>>      case SDHC_CTRL_ADMA1_32:
>> -        dma_memory_read(&address_space_memory, entry_addr, (uint8_t 
>> *)&adma1,
>> -                        sizeof(adma1));
>> -        adma1 = le32_to_cpu(adma1);
>> +        adma1 = ldl_le_dma(&address_space_memory, entry_addr);
>>          dscr->addr = (hwaddr)(adma1 & 0xFFFFF000);
>>          dscr->attr = (uint8_t)extract32(adma1, 0, 7);
>>          dscr->incr = 4;
>> @@ -633,14 +629,9 @@ static void get_adma_description(SDHCIState *s, 
>> ADMADescr *dscr)
>>          }
>>          break;
>>      case SDHC_CTRL_ADMA2_64:
>> -        dma_memory_read(&address_space_memory, entry_addr,
>> -                        (uint8_t *)(&dscr->attr), 1);
>> -        dma_memory_read(&address_space_memory, entry_addr + 2,
>> -                        (uint8_t *)(&dscr->length), 2);
>> -        dscr->length = le16_to_cpu(dscr->length);
>> -        dma_memory_read(&address_space_memory, entry_addr + 4,
>> -                        (uint8_t *)(&dscr->addr), 8);
>> -        dscr->attr = le64_to_cpu(dscr->attr);
>
>> +        dscr->attr = ldub_dma(&address_space_memory, entry_addr);
>> +        dscr->length = lduw_le_dma(&address_space_memory, entry_addr + 2);
>> +        dscr->attr = ldq_le_dma(&address_space_memory, entry_addr + 4);
>
> Why this is being overwritten?

Do you mean 'rewritten'?

> It looks like you have dropped an addr as well.

Which addr? The diff is a bit compressed, if you separate it is more obvious:

 -        dma_memory_read(&address_space_memory, entry_addr,
 -                        (uint8_t *)(&dscr->attr), 1);
 +        dscr->attr = ldub_dma(&address_space_memory, entry_addr);


 -        dma_memory_read(&address_space_memory, entry_addr + 2,
 -                        (uint8_t *)(&dscr->length), 2);
 -        dscr->length = le16_to_cpu(dscr->length);
 +        dscr->length = lduw_le_dma(&address_space_memory, entry_addr + 2);


 -        dma_memory_read(&address_space_memory, entry_addr + 4,
 -                        (uint8_t *)(&dscr->addr), 8);
 -        dscr->attr = le64_to_cpu(dscr->attr);
 +        dscr->attr = ldq_le_dma(&address_space_memory, entry_addr + 4);

The API is detailled in this file: docs/devel/loads-stores.rst

I decided to rewrite this code with this API because it looks easier
to understand (maybe once you read the API doc), so easier to review
:)