Claude review: drm/bridge: Add Lontium LT7911EXC eDP to MIPI DSI bridge

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

**HIGH: `bridge->dev = NULL` in `.detach` is incorrect**

```c
static void lt7911exc_bridge_detach(struct drm_bridge *bridge)
{
	struct lt7911exc *lt7911exc = bridge_to_lt7911exc(bridge);

	guard(mutex)(&lt7911exc->ocm_lock);
	bridge->dev = NULL;
}
```

No other bridge driver in the kernel sets `bridge->dev = NULL` in its `.detach` callback. This field is managed by the DRM core. The motivation appears to be preventing `drm_kms_helper_hotplug_event(lt7911exc->bridge.dev)` in the firmware upgrade worker from being called after detach, but the correct approach is to check the driver's own state (e.g., the `removed` flag or a dedicated `attached` flag) rather than corrupting framework state.

**HIGH: Firmware upgrade error paths leave MCU halted**

In `lt7911exc_firmware_upgrade_work`, after `lt7911exc_hw_mcu_halt()` is called, the error paths for `lt7911exc_block_erase`, `lt7911exc_write_data`, and `lt7911exc_write_crc` all jump to `out_release_fw` without restarting the MCU or resetting the chip:

```c
	lt7911exc_reset(lt7911exc);

	mutex_lock(&lt7911exc->ocm_lock);
	lt7911exc_hw_mcu_halt(lt7911exc);
	mutex_unlock(&lt7911exc->ocm_lock);

	ret = lt7911exc_block_erase(lt7911exc);
	if (ret) {
		dev_err(dev, "failed to block erase.\n");
		goto out_release_fw;  /* MCU left halted, device bricked until next probe */
	}
```

After a failed erase or write, the device is left with MCU halted and potentially partially-erased flash. A `lt7911exc_reset()` or `lt7911exc_hw_mcu_run()` call should be added to error recovery paths.

**MEDIUM: Redundant `dev_set_drvdata` and `i2c_set_clientdata`**

Both are called in probe:
```c
	dev_set_drvdata(dev, lt7911exc);
	...
	i2c_set_clientdata(client, lt7911exc);
```

`i2c_set_clientdata(client, data)` is equivalent to `dev_set_drvdata(&client->dev, data)`, so the `dev_set_drvdata` call is redundant. Only `i2c_set_clientdata` is needed (and `i2c_get_clientdata` is already used in `remove`).

**MEDIUM: Unchecked `regmap_write` return values in `lt7911exc_write_data`**

The short-write handling and page commit in the write loop don't check return values:

```c
		//write method for less than LT_PAGE_SIZE bytes.
		if (page_len < LT_PAGE_SIZE) {
			regmap_write(lt7911exc->regmap, 0x5f, 0x05);
			regmap_write(lt7911exc->regmap, 0x5f, 0x01);
			//hardware requires delay
			usleep_range(1000, 2000);
		}

		regmap_write(lt7911exc->regmap, 0x5f, 0x00);
```

All three `regmap_write` calls should have their return values checked, especially during a flash programming sequence where an I2C failure could corrupt firmware.

**MEDIUM: Sysfs attribute naming convention**

```c
static DEVICE_ATTR_RW(lt7911exc_firmware);
```

The sysfs attribute will be named `lt7911exc_firmware`. The kernel convention is to not prefix attributes with the driver name since they already live under the device's sysfs directory. Something like `firmware_upgrade` (with a matching `firmware_upgrade_store`/`firmware_upgrade_show`) would be more conventional.

**MEDIUM: `sysfs_emit` format mismatch for firmware version**

```c
	return sysfs_emit(buf, "0x%04x\n", version);
```

But `lt7911exc_read_version` returns a 3-byte value `(buf[0] << 16) | (buf[1] << 8) | buf[2]`, which can be up to 0xFFFFFF (6 hex digits). The `%04x` format would display all digits but the `04` minimum width padding suggests the author expects 4 digits. Use `0x%06x` if the version is always 3 bytes.

**LOW: Kconfig help text formatting**

```
	  chip.The LT7911EXC converts eDP input to MIPI
```

Missing space after the period: should be `chip. The LT7911EXC`.

**LOW: C++ style comments**

Several places use `//` comments which violate kernel coding style:

```c
	//enable mipi stream
	...
	//disable mipi stream
	...
	//write method for less than LT_PAGE_SIZE bytes.
	...
	//hardware requires delay
```

These should all use `/* */` style comments per the kernel coding standard.

**LOW: `u64` types for small address values**

`lt7911exc_prog_init` and `lt7911exc_write_data` use `u64 addr` and `u64 size`/`u64 offset`, but the flash is only 64KB (`FW_SIZE = 64 * 1024`). `u32` is more than sufficient and avoids unnecessary widening on 32-bit platforms.

**LOW: Missing explicit `#include <linux/workqueue.h>`**

The driver uses `INIT_WORK`, `schedule_work`, and `cancel_work_sync` but does not directly include `<linux/workqueue.h>`. It works via transitive includes but should be explicit.

**OBSERVATION: `lt7911exc_block_erase` redundantly halts MCU**

`lt7911exc_block_erase` internally writes `0xee = 0x01` (MCU halt), but the caller `lt7911exc_firmware_upgrade_work` already calls `lt7911exc_hw_mcu_halt` before `lt7911exc_block_erase`. This isn't a bug but suggests the erase function's register sequence was written independently of the surrounding flow. Consider whether the redundant halt is intentional for robustness or an oversight.

**OBSERVATION: `lt7911exc_upgrade_result` error message**

```c
		dev_err(dev, "Failed to switch to page 0xe0 in prog_init: %d\n", ret);
```

The function is `lt7911exc_upgrade_result`, not `prog_init`. This looks like a copy-paste artifact from `lt7911exc_prog_init`.

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Generated by Claude Code Patch Reviewer