[PATCH v7 6/9] hwmon: pmbus: adm1266: Add group command support

[<alexandru.tachici@analog.com>]

From: Alexandru Tachici <alexandru.tachici@analog.com>

The Group Command Protocol is used to send commands
to more than one PMBus device. Some devices working
together require that they must execute some commands
all at once.

The commands are sent in one continuous transmission.
When the devices detect the STOP condition that ends
the sending of commands, they all begin executing
the command they received.

This patch adds support for the group command protocol.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/hwmon/pmbus/adm1266.c | 50 +++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/drivers/hwmon/pmbus/adm1266.c b/drivers/hwmon/pmbus/adm1266.c
index b61a968d67f9..f571fe1ee35d 100644
--- a/drivers/hwmon/pmbus/adm1266.c
+++ b/drivers/hwmon/pmbus/adm1266.c
@@ -73,6 +73,56 @@ static const struct nvmem_cell_info adm1266_nvmem_cells[] = {
 
 DECLARE_CRC8_TABLE(pmbus_crc_table);
 
+/* PMBus Group command. */
+static int adm1266_pmbus_group_command(struct adm1266_data *data, struct i2c_client **clients,
+				       u8 nr_clients, u8 cmd, u8 w_len, u8 *data_w)
+{
+	struct i2c_msg *msgs;
+	u8 addr;
+	int ret;
+	int i;
+
+	msgs = kcalloc(nr_clients, sizeof(struct i2c_msg), GFP_KERNEL);
+	if (!msgs)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_clients; i++) {
+		msgs[i].addr = clients[i]->addr;
+		msgs[i].len = w_len + 1;
+
+		msgs[i].buf = kcalloc(ADM1266_PMBUS_BLOCK_MAX + 2, sizeof(u8), GFP_KERNEL);
+		if (!msgs[i].buf) {
+			ret = -ENOMEM;
+			goto cleanup;
+		}
+
+		msgs[i].buf[0] = cmd;
+		memcpy(&msgs[i].buf[1], data_w, w_len);
+
+		if (clients[i]->flags & I2C_CLIENT_PEC) {
+			u8 crc = 0;
+
+			addr = i2c_8bit_addr_from_msg(&msgs[i]);
+			crc = crc8(pmbus_crc_table, &addr, 1, crc);
+			crc = crc8(pmbus_crc_table, msgs[i].buf, msgs[i].len,
+				   crc);
+
+			msgs[i].buf[msgs[i].len] = crc;
+			msgs[i].len++;
+		}
+	};
+
+	ret = i2c_transfer(data->client->adapter, msgs, nr_clients);
+
+cleanup:
+	for (i = i - 1; i >= 0; i--)
+		kfree(msgs[i].buf);
+
+	kfree(msgs);
+
+	return ret;
+}
+
 /*
  * Different from Block Read as it sends data and waits for the slave to
  * return a value dependent on that data. The protocol is simply a Write Block
-- 
2.20.1