[PATCH v3] platform/chrome: Add cros_ec_readmem() helpers for I2C/SPI based ECs

[Moritz Fischer <mdf@kernel.org>]

Add cros_ec_readmem() helpers for I2C/SPI based ECs.
Unlike the LPC based ECs the I2C/SPI based ones cannot just directly
read the mapped region, but have to resort to EC_CMD_READ_MEMMAP.

This is useful for things like accessing fan speeds or temperatures.

Signed-off-by: Moritz Fischer <mdf@kernel.org>
---

Hi all,

This can be used for a hwmon or thermal driver such as [1], but also
alone can be used with 'ectool' via the ioctl() interface.

Thanks,
Moritz


Changes from v2:
- Addressed KBuild complaint about max() with size_t vs unsigned int
  parameters

Changes from v1:
- Moved to drivers/platform/proto


[1] https://patchwork.kernel.org/patch/9670517/ (needs work)
---
 drivers/platform/chrome/cros_ec_i2c.c   |  1 +
 drivers/platform/chrome/cros_ec_proto.c | 39 +++++++++++++++++++++++++
 drivers/platform/chrome/cros_ec_spi.c   |  1 +
 include/linux/mfd/cros_ec.h             | 12 ++++++++
 4 files changed, 53 insertions(+)

diff --git a/drivers/platform/chrome/cros_ec_i2c.c b/drivers/platform/chrome/cros_ec_i2c.c
index ef9b4763356f..c3a9bee37b1d 100644
--- a/drivers/platform/chrome/cros_ec_i2c.c
+++ b/drivers/platform/chrome/cros_ec_i2c.c
@@ -303,6 +303,7 @@ static int cros_ec_i2c_probe(struct i2c_client *client,
 	ec_dev->irq = client->irq;
 	ec_dev->cmd_xfer = cros_ec_cmd_xfer_i2c;
 	ec_dev->pkt_xfer = cros_ec_pkt_xfer_i2c;
+	ec_dev->cmd_readmem = cros_ec_readmem;
 	ec_dev->phys_name = client->adapter->name;
 	ec_dev->din_size = sizeof(struct ec_host_response_i2c) +
 			   sizeof(struct ec_response_get_protocol_info);
diff --git a/drivers/platform/chrome/cros_ec_proto.c b/drivers/platform/chrome/cros_ec_proto.c
index cc7baf0ecb3c..d2ba662fc713 100644
--- a/drivers/platform/chrome/cros_ec_proto.c
+++ b/drivers/platform/chrome/cros_ec_proto.c
@@ -636,3 +636,42 @@ u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev)
 	return host_event;
 }
 EXPORT_SYMBOL(cros_ec_get_host_event);
+
+int cros_ec_readmem(struct cros_ec_device *ec, unsigned int offset,
+		    unsigned int bytes, void *dest)
+{
+	struct ec_params_read_memmap *params;
+	struct cros_ec_command *msg;
+	int ret;
+
+	if (offset >= EC_MEMMAP_SIZE - bytes)
+		return -EINVAL;
+
+	msg = kzalloc(sizeof(*msg) + max_t(size_t, sizeof(*params), bytes),
+		      GFP_KERNEL);
+	if (!msg)
+		return -ENOMEM;
+
+	msg->version = 0;
+	msg->command = EC_CMD_READ_MEMMAP;
+	msg->insize = bytes;
+	msg->outsize = sizeof(*params);
+
+	params = (struct ec_params_read_memmap *)msg->data;
+	params->offset = offset;
+	params->size = bytes;
+
+	ret = cros_ec_cmd_xfer_status(ec, msg);
+	if (ret < 0) {
+		dev_warn(ec->dev, "cannot read mapped reg: %d/%d\n",
+			 ret, msg->result);
+		goto out_free;
+	}
+
+	memcpy(dest, msg->data, bytes);
+
+out_free:
+	kfree(msg);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cros_ec_readmem);
diff --git a/drivers/platform/chrome/cros_ec_spi.c b/drivers/platform/chrome/cros_ec_spi.c
index 2060d1483043..b95c1a25adfc 100644
--- a/drivers/platform/chrome/cros_ec_spi.c
+++ b/drivers/platform/chrome/cros_ec_spi.c
@@ -666,6 +666,7 @@ static int cros_ec_spi_probe(struct spi_device *spi)
 	ec_dev->irq = spi->irq;
 	ec_dev->cmd_xfer = cros_ec_cmd_xfer_spi;
 	ec_dev->pkt_xfer = cros_ec_pkt_xfer_spi;
+	ec_dev->cmd_readmem = cros_ec_readmem;
 	ec_dev->phys_name = dev_name(&ec_spi->spi->dev);
 	ec_dev->din_size = EC_MSG_PREAMBLE_COUNT +
 			   sizeof(struct ec_host_response) +
diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
index de8b588c8776..0228fb42dcda 100644
--- a/include/linux/mfd/cros_ec.h
+++ b/include/linux/mfd/cros_ec.h
@@ -335,6 +335,18 @@ int cros_ec_get_next_event(struct cros_ec_device *ec_dev, bool *wake_event);
  */
 u32 cros_ec_get_host_event(struct cros_ec_device *ec_dev);
 
+/**
+ * cros_ec_readmem - Read mapped memory in the ChromeOS EC
+ *
+ * @ec: Device to read from
+ * @offset: Offset to read within the mapped region
+ * @bytes: number of bytes to read
+ * @data: Return data
+ * @return: 0 if Ok, -ve on error
+ */
+int cros_ec_readmem(struct cros_ec_device *ec, unsigned int offset,
+		    unsigned int bytes, void *dest);
+
 /* sysfs stuff */
 extern struct attribute_group cros_ec_attr_group;
 extern struct attribute_group cros_ec_lightbar_attr_group;
-- 
2.20.1