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SubjectRe: [PATCH] i2c/busses: (mpc) Add support for SMBUS_READ_BLOCK_DATA
On Wed, 16 Nov 2011 09:28:29 -0800, York Sun wrote:
> I am not sure if this mail will reach the list as I am not subscribed.
>
> In the v2 patch (actually both version), you wrote
>
> > + byte = readb(i2c->base + MPC_I2C_DR);
> > +
> > + /* Adjust length if first received byte is length */
> > + if (i == 0 && recv_len) {
> > + if (byte == 0 || byte > I2C_SMBUS_BLOCK_MAX)
> > + return -EPROTO;
> > + length += byte;
> > + /*
> > + * For block reads, generate txack here if data length
> > + * is 1 byte (total length is 2 bytes).
> > + */
> > + if (length == 2)
> > + writeccr(i2c, CCR_MIEN | CCR_MEN | CCR_MSTA
> > + | CCR_TXAK);
> > + }
> > + data[i] = byte;
>
> I am wondering if the first byte should be left out for data[] if the
> recv_len is non-zero. If I understand correctly, this patch is to
> support of SMBus with multiple byte read. The SMBus is different from
> I2C bus on multiple byte. The first data is byte count vs slave data for
> I2C. So you will receive all data preceded by the byte count, which is
> one more than your loop.

That's why he wrote

length += byte;

and not

length = byte;

length is initialized to 1 for SMBus block reads.

--
Jean Delvare


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