* [PATCH v4 2/2] platform: chrome: lightbar: Add support for large sequence
2026-01-30 8:13 [PATCH v4 1/2] platform: chrome: lightbar: Report number of segments Gwendal Grignou
@ 2026-01-30 8:13 ` Gwendal Grignou
2026-01-30 8:32 ` [PATCH v4 1/2] platform: chrome: lightbar: Report number of segments Tzung-Bi Shih
1 sibling, 0 replies; 3+ messages in thread
From: Gwendal Grignou @ 2026-01-30 8:13 UTC (permalink / raw)
To: tzungbi; +Cc: chrome-platform, Gwendal Grignou
Current sequences are limited to 192 bytes. Increase support to whatever
the EC support. If the sequence is too long, the EC will return an
OVERFLOW error.
Test: Check sending a large sequence is received by the EC.
Signed-off-by: Gwendal Grignou <gwendal@google.com>
---
Changes in v4:
- Cleanup calculation of the header size by using offsetof macro.
Changes in v3:
- Fix allocation size for lightbar command. Use the maximal allowed
sizes by default.
Changes in v2:
- Default initilization for lb_version.
- Minimal changes in local variables definitions in program_store().
- Fix errors in cros_ec_commands.h: use a variable length array for
payload.
drivers/platform/chrome/cros_ec_lightbar.c | 88 +++++++++++++------
.../linux/platform_data/cros_ec_commands.h | 13 +++
2 files changed, 74 insertions(+), 27 deletions(-)
diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c
index 5f14c7425faf..463383bd9076 100644
--- a/drivers/platform/chrome/cros_ec_lightbar.c
+++ b/drivers/platform/chrome/cros_ec_lightbar.c
@@ -30,6 +30,11 @@ static unsigned long lb_interval_jiffies = 50 * HZ / 1000;
*/
static bool userspace_control;
+/*
+ * Lightbar version
+ */
+static int lb_version;
+
static ssize_t interval_msec_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -86,11 +91,8 @@ static int lb_throttle(void)
static struct cros_ec_command *alloc_lightbar_cmd_msg(struct cros_ec_dev *ec)
{
+ int len = max(ec->ec_dev->max_response, ec->ec_dev->max_request);
struct cros_ec_command *msg;
- int len;
-
- len = max(sizeof(struct ec_params_lightbar),
- sizeof(struct ec_response_lightbar));
msg = kmalloc(sizeof(*msg) + len, GFP_KERNEL);
if (!msg)
@@ -98,6 +100,11 @@ static struct cros_ec_command *alloc_lightbar_cmd_msg(struct cros_ec_dev *ec)
msg->version = 0;
msg->command = EC_CMD_LIGHTBAR_CMD + ec->cmd_offset;
+ /*
+ * Default sizes for regular commands.
+ * Can be set smaller to optimize transfer,
+ * larger when sending large light sequences.
+ */
msg->outsize = sizeof(struct ec_params_lightbar);
msg->insize = sizeof(struct ec_response_lightbar);
@@ -464,10 +471,11 @@ static ssize_t sequence_store(struct device *dev, struct device_attribute *attr,
static ssize_t program_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
- int extra_bytes, max_size, ret;
+ size_t extra_bytes, max_size;
struct ec_params_lightbar *param;
struct cros_ec_command *msg;
struct cros_ec_dev *ec = to_cros_ec_dev(dev);
+ int ret;
/*
* We might need to reject the program for size reasons. The EC
@@ -475,14 +483,22 @@ static ssize_t program_store(struct device *dev, struct device_attribute *attr,
* and send a program that is too big for the protocol. In order
* to ensure the latter, we also need to ensure we have extra bytes
* to represent the rest of the packet.
+ * With V3, larger program can be sent, limited only by the EC.
+ * Only the protocol limit the payload size.
*/
- extra_bytes = sizeof(*param) - sizeof(param->set_program.data);
- max_size = min(EC_LB_PROG_LEN, ec->ec_dev->max_request - extra_bytes);
- if (count > max_size) {
- dev_err(dev, "Program is %u bytes, too long to send (max: %u)",
- (unsigned int)count, max_size);
-
- return -EINVAL;
+ if (lb_version < 3) {
+ extra_bytes = sizeof(*param) - sizeof(param->set_program.data);
+ max_size = min(EC_LB_PROG_LEN, ec->ec_dev->max_request - extra_bytes);
+ if (count > max_size) {
+ dev_err(dev, "Program is %zu bytes, too long to send (max: %zu)",
+ count, max_size);
+
+ return -EINVAL;
+ }
+ } else {
+ extra_bytes = offsetof(typeof(*param), set_program_ex) +
+ sizeof(param->set_program_ex);
+ max_size = ec->ec_dev->max_request - extra_bytes;
}
msg = alloc_lightbar_cmd_msg(ec);
@@ -492,26 +508,44 @@ static ssize_t program_store(struct device *dev, struct device_attribute *attr,
ret = lb_throttle();
if (ret)
goto exit;
+ param = (struct ec_params_lightbar *)msg->data;
- dev_info(dev, "Copying %zu byte program to EC", count);
+ if (lb_version < 3) {
+ dev_info(dev, "Copying %zu byte program to EC", count);
- param = (struct ec_params_lightbar *)msg->data;
- param->cmd = LIGHTBAR_CMD_SET_PROGRAM;
+ param->cmd = LIGHTBAR_CMD_SET_PROGRAM;
- param->set_program.size = count;
- memcpy(param->set_program.data, buf, count);
+ param->set_program.size = count;
+ memcpy(param->set_program.data, buf, count);
- /*
- * We need to set the message size manually or else it will use
- * EC_LB_PROG_LEN. This might be too long, and the program
- * is unlikely to use all of the space.
- */
- msg->outsize = count + extra_bytes;
+ /*
+ * We need to set the message size manually or else it will use
+ * EC_LB_PROG_LEN. This might be too long, and the program
+ * is unlikely to use all of the space.
+ */
+ msg->outsize = count + extra_bytes;
- ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
- if (ret < 0)
- goto exit;
+ ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
+ if (ret < 0)
+ goto exit;
+ } else {
+ size_t offset = 0;
+ size_t payload = 0;
+
+ param->cmd = LIGHTBAR_CMD_SET_PROGRAM_EX;
+ while (offset < count) {
+ payload = min(max_size, count - offset);
+ param->set_program_ex.offset = offset;
+ param->set_program_ex.size = payload;
+ memcpy(param->set_program_ex.data, &buf[offset], payload);
+ msg->outsize = payload + extra_bytes;
+ ret = cros_ec_cmd_xfer_status(ec->ec_dev, msg);
+ if (ret < 0)
+ goto exit;
+ offset += payload;
+ }
+ }
ret = count;
exit:
kfree(msg);
@@ -589,7 +623,7 @@ static int cros_ec_lightbar_probe(struct platform_device *pd)
* Ask then for the lightbar version, if it's 0 then the 'cros_ec'
* doesn't have a lightbar.
*/
- if (!get_lightbar_version(ec_dev, NULL, NULL))
+ if (!get_lightbar_version(ec_dev, &lb_version, NULL))
return -ENODEV;
/* Take control of the lightbar from the EC. */
diff --git a/include/linux/platform_data/cros_ec_commands.h b/include/linux/platform_data/cros_ec_commands.h
index 9cbf024f56c3..144243143034 100644
--- a/include/linux/platform_data/cros_ec_commands.h
+++ b/include/linux/platform_data/cros_ec_commands.h
@@ -2020,6 +2020,17 @@ struct lightbar_program {
uint8_t data[EC_LB_PROG_LEN];
} __ec_todo_unpacked;
+/*
+ * Lightbar program for large sequences. Sequences are sent in pieces, with
+ * increasing offset. The sequences are still limited by the amount reserved in
+ * EC RAM.
+ */
+struct lightbar_program_ex {
+ uint16_t offset;
+ uint8_t size;
+ uint8_t data[0];
+} __ec_todo_unpacked;
+
struct ec_params_lightbar {
uint8_t cmd; /* Command (see enum lightbar_command) */
union {
@@ -2066,6 +2077,7 @@ struct ec_params_lightbar {
struct lightbar_params_v2_colors set_v2par_colors;
struct lightbar_program set_program;
+ struct lightbar_program_ex set_program_ex;
};
} __ec_todo_packed;
@@ -2154,6 +2166,7 @@ enum lightbar_command {
LIGHTBAR_CMD_GET_PARAMS_V2_COLORS = 32,
LIGHTBAR_CMD_SET_PARAMS_V2_COLORS = 33,
LIGHTBAR_CMD_GET_PARAMS_V3 = 34,
+ LIGHTBAR_CMD_SET_PROGRAM_EX = 35,
LIGHTBAR_NUM_CMDS
};
--
2.53.0.rc1.225.gd81095ad13-goog
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