From: Wolfram Sang <wsa@kernel.org>
To: daniel.stodden@gmail.com
Cc: linux-i2c@vger.kernel.org, jdelvare@suse.de,
Daniel Stodden <dns@arista.com>
Subject: Re: [RFC PATCH] i2c: Support Smbus 3.0 block sizes up to 255 bytes.
Date: Tue, 28 Jul 2020 13:16:02 +0200 [thread overview]
Message-ID: <20200728111602.GC980@ninjato> (raw)
In-Reply-To: <20200728004708.4430-1-daniel.stodden@gmail.com>
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> * Allocated bit 4 (I2C_SMBUS3_BLOCK=0x10), to simplify Smbus2
> compatibility: I2C_SMBUS_*BLOCK* = (<old type>|0x10)
I think the code becomes easier to understand, if we use new transfer
types a bit more explicitly. Also, I am not sure of the extra bit
because it is not clearly visible that types >= 16 and <= 31 will have a
special meaning. We could do like this if we sacrifice one number for
an unused BROKEN with 255 byte:
-#define I2C_SMBUS_BLOCK_DATA 5
+#define I2C_SMBUS2_BLOCK_DATA 5 /* 32 byte only, deprecated */
-#define I2C_SMBUS_I2C_BLOCK_BROKEN 6
+#define I2C_SMBUS2_I2C_BLOCK_BROKEN 6 /* 32 byte only, deprecated */
-#define I2C_SMBUS_BLOCK_PROC_CALL 7 /* SMBus 2.0 */
+#define I2C_SMBUS2_BLOCK_PROC_CALL 7 /* SMBus 2.0, 32 byte only, deprecated */
-#define I2C_SMBUS_I2C_BLOCK_DATA 8
+#define I2C_SMBUS2_I2C_BLOCK_DATA 8 /* 32 byte only, deprecated */
+#define I2C_SMBUS_BLOCK_DATA 9
+#define I2C_SMBUS_I2C_BLOCK_BROKEN 10 /* FIXME: probably say "don't use" here
+#define I2C_SMBUS_BLOCK_PROC_CALL 11 /* SMBus >= 2.0 */
+#define I2C_SMBUS_I2C_BLOCK_DATA 12
>
> + user_len = kmalloc_array(nmsgs, sizeof(*user_len), GFP_KERNEL);
> + if (!user_len) {
> + res = -ENOMEM;
> + goto out;
> + }
Maybe on stack? I2C_RDWR_IOCTL_MAX_MSGS will ensure this will stay at a
sane value.
> @@ -313,7 +357,19 @@ static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
> union i2c_smbus_data __user *data)
> {
> union i2c_smbus_data temp = {};
> - int datasize, res;
> + int block_max, datasize, res;
> +
'size' is really a misleading name :(
+ if (size <= I2C_SMBUS2_I2C_BLOCK_DATA) {
+ if (size >= I2C_SMBUS2_BLOCK_DATA)
+ size += I2C_SMBUS_BLOCK_DATA - I2C_SMBUS2_BLOCK_DATA;
+ block_max = I2C_SMBUS_BLOCK_MAX;
+ } else {
+ block_max = I2C_SMBUS3_BLOCK_MAX;
+ }
Would this work, too?
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next prev parent reply other threads:[~2020-07-28 11:16 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-28 0:47 [RFC PATCH] i2c: Support Smbus 3.0 block sizes up to 255 bytes daniel.stodden
2020-07-28 9:40 ` Wolfram Sang
2020-07-28 10:18 ` Daniel Stodden
2020-07-28 10:36 ` Wolfram Sang
2020-07-28 11:27 ` Daniel Stodden
2020-07-28 17:04 ` Jean Delvare
2020-07-28 21:16 ` Daniel Stodden
2020-07-29 10:51 ` Wolfram Sang
2020-07-28 11:16 ` Wolfram Sang [this message]
2020-07-28 11:40 ` Daniel Stodden
2020-07-28 12:46 ` Daniel Stodden
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