Re: Adding SMBus block transfers to iic(4)

[Paul Goyette <paul%whooppee.com@localhost>]

Just an update here.

In order to enable requesting block-mode transfers using the 
I2C_IOCTL_EXEC method from userland, I'm now proposing to add two new 
"high-level operations" to the i2c_op_t enum, along with a new macro 
predicate:

typedef enum {
        I2C_OP_READ_WITH_STOP   = 1,
        I2C_OP_WRITE            = 2,
        I2C_OP_WRITE_WITH_STOP  = 3,
+       I2C_OP_READ_BLOCK       = 5,    /* All block operations imply STOP */
+       I2C_OP_WRITE_BLOCK      = 7
 } i2c_op_t;

 #define        I2C_OP_READ_P(x)        (((int)(x) & 2) == 0)
 #define        I2C_OP_WRITE_P(x)       (! I2C_OP_READ_P(x))
 #define        I2C_OP_STOP_P(x)        (((int)(x) & 1) != 0)
+#define        I2C_OP_BLKMODE_P(x)     (((int)(x) & 4) != 0)



On Sun, 11 Mar 2012, Paul Goyette wrote:

> There are apparently some devices out there that really need to have i2c 
> block-mode transfers, and it appears that none of our current drivers (at 
> least, none of the "mainstream" pci drivers) supports this.
>
> At first glance, it might appear that we could simply check the transfer
> requested byte-count, and automatically operate in block mode if the count is 
> greater than 2;  the implication is that we could fall back to byte or word 
> transfers for smaller byte counts.  But it looks like at least one device out 
> there [1] doesn't support this.
>
> So I propose adding a new flag bit that can be passed to iic_exec() to 
> request block-transfer protocols.  In src/sys/dev/i2c/i2c_io.h
>
>         #define I2C_F_BLOCK     0x20
>
> Comments?  Suggestions?  Alternatives?
>
>
>
> [1] http://eeepc-linux.googlecode.com/files/9LPR426A.pdf
>
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> | Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:       |
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> | Network Engineer | 0786 F758 55DE 53BA 7731 | pgoyette at juniper.net |
> | Kernel Developer |                          | pgoyette at netbsd.org  |
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| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:       |
| Customer Service | FA29 0E3B 35AF E8AE 6651 | paul at whooppee.com    |
| Network Engineer | 0786 F758 55DE 53BA 7731 | pgoyette at juniper.net |
| Kernel Developer |                          | pgoyette at netbsd.org  |
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