jklincn opened a new pull request, #18164:
URL: https://github.com/apache/nuttx/pull/18164
## Summary
This PR fixes the `read` method in the `dhtxx` character driver to comply
with standard POSIX behavior.
* **Why**: The driver currently returns `0` on success, which does not
conform to the standard `read` interface (which should return the number of
bytes read). Additionally, it uses non-standard or incorrect error codes (e.g.,
returning `-ENOSYS` for invalid arguments or generic `-1`).
* **What**:
1. Updated `dhtxx_read` to return the actual number of bytes read
(`sizeof(struct dhtxx_sensor_data_s)`) on success.
2. Replaced generic `-1` and incorrect `-ENOSYS` with standard errno:
* `-EINVAL` for invalid buffer arguments.
* `-ETIMEDOUT` for sensor timeouts.
* `-EIO` for checksum verification or parsing failures.
## Impact
* **Is new feature added?** NO
* **Impact on user?** YES. Applications checking the return value of
`read()` will now receive the correct byte count instead of `0`.
* **Impact on build?** NO
* **Impact on hardware?** NO
* **Impact on documentation?** NO
* **Impact on security?** NO
* **Impact on compatibility?** YES. Improves POSIX compatibility and
standard driver behavior.
## Testing
I confirm that changes are verified on local setup and works as intended:
* **Build Host(s):** Linux (Ubuntu), x86_64, arm-none-eabi-gcc
* **Target(s):** STM32F103ZET6 (Custom Board), DHT11 Sensor
**Testing logs before change:**
```
NuttShell (NSH) NuttX-12.12.0
nsh> dht11
Reading DHT11...
Read failed. ret=0
nsh>
```
**Testing logs after change:**
```
NuttShell (NSH) NuttX-12.12.0
nsh> dht11
Reading DHT11...
Humidity: 21.0 %
Temperature: 24.0 C
nsh>
```
Test Source Code `dht11`:
```c
#include <fcntl.h>
#include <nuttx/config.h>
#include <nuttx/sensors/dhtxx.h>
#include <stdio.h>
#include <unistd.h>
int main(int argc, char *argv[]) {
int fd;
struct dhtxx_sensor_data_s data;
ssize_t ret;
fd = open("/dev/dht0", O_RDONLY);
if (fd < 0) {
printf("Failed to open /dev/dht0\n");
return -1;
}
printf("Reading DHT11...\n");
// Read data from DHT11 sensor
ret = read(fd, &data, sizeof(data));
if (ret != sizeof(data)) {
printf("Read failed. ret=%zd\n", ret);
} else {
if (data.status == DHTXX_SUCCESS) {
printf("Humidity: %.1f %%\n", data.hum);
printf("Temperature: %.1f C\n", data.temp);
} else {
printf("Sensor Error Status: %d\n", data.status);
}
}
close(fd);
return 0;
}
```
## PR verification Self-Check
* [x] This PR introduces only one functional change.
* [x] I have updated all required description fields above.
* [x] My PR adheres to Contributing
[Guidelines](https://github.com/apache/nuttx/blob/master/CONTRIBUTING.md) and
[Documentation](https://nuttx.apache.org/docs/latest/contributing/index.html)
(git commit title and message, coding standard, etc).
* [ ] My PR is still work in progress (not ready for review).
* [x] My PR is ready for review and can be safely merged into a codebase.
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