Re: [PATCH v3 3/3] New I2C: Add support for TPM devices over I2C bus

[Stefan Berger <stefanb@linux.ibm.com>]

On 3/24/23 04:24, Cédric Le Goater wrote:
> Hello Ninad,
> 

>> +
>> +/*
>> + * Convert little endian byte stream into local formated
>> + * unsigned integer
>> + */
>> +static inline uint32_t tpm_i2c_le_bytes_to_uint(TPMStateI2C *i2cst)
>> +{
>> +    uint32_t data = 0;
>> +    int      i;
>> +
>> +    assert(i2cst->offset <= 5);  /* Including 0th register value */
>> +
>> +    if (tpm_i2c_is_little_endian()) {
>> +        for (i = 1; i < i2cst->offset; i++) {
>> +            data |= (((uint32_t)i2cst->data[i]) << (8 * (i - 1)));
>> +        }
>> +    } else {
>> +        for (i = 1; i < i2cst->offset; i++) {
>> +            data <<= 8;
>> +            data |= i2cst->data[i];
>> +        }
>> +    }
>> +
>> +    return data;
>> +}
> 
> Why is this endianess test  needed ? Something looks wrong.
> 
> Could you please explain the endianess used by the various devices and
> the endianness of the MMIO ops ?
> 
> If you want to test on a BE host, simply install a debian PPC64 VM/LPAR
> on a POWER9/10 box. I suppose you have access to one in IBM.

I found it's not that simple anymore since all distros moved to little endian. I have been using Fedora 28 for big endian tests for swtpm but I have never tried it with QEMU...

    Stefan