Re: Adding support for QMC5883L magnetometer to IIO subsystem

[David Lechner <dlechner@baylibre.com>]

On 4/8/25 9:13 AM, Brajesh Patil wrote:
> I have a QMC5883L magnetometer module that I’ve been trying to integrate with my 
> Raspberry Pi using a kernel-space driver. While checking the mainline kernel, I 
> found that there is a driver for the HMC5883L (under the hmc5843 driver), but nothing 
> for QMC5883L.
> 
> I compared the datasheets for both devices and confirmed that they are not 
> register-compatible — the QMC5883L has a different I2C address and an entirely different 
> register map from the HMC5883L.
> 
> Given that this sensor is widely used (often as a drop-in replacement for the 
> now-discontinued HMC5883L), I was thinking of writing a new driver for it under the IIO 
> subsystem.
> 
> Would it make sense to move forward with this? If so, I’d appreciate any guidance or 
> suggestions from the community.
> 
> Thanks,  
> Brajesh 
> 
> 

Go for it. :-)

My advice for writing a new driver: Don't try to implement every feature in one
patch (or even one patch series). Just start with the most basic functionality.
Then add more features in separate patches as they are needed. (Devicetree
bindings are an exception and should be as complete as possible in the first
patch.)