Hi, On 23/01/15 14:05, Baluta, Teodora wrote: ... >>>>>>> So why not v4l? These are effectively image sensors.. >>>>>> >>>>>> Well, here's why I don't think v4l would be the best option: >>>>>> >>>>>> - an image scanner could be implemented in the v4l subsystem, but >>>>>> it seems far more complicated for a simple fingerprint scanner - it >>>>>> usually has drivers for webcams, TVs or video streaming devices. >>>>>> The v4l subsystem (with all its support for colorspace, decoders, >>>>>> image compression, frame control) seems a bit of an overkill for a >>>>>> very straightforward fingerprint imaging sensor. >>> >>>> Whilst those are there, I would doubt the irrelevant bits would put >>>> much burden on a fingerprint scanning driver. Been a while since I >>>> did anything in that area though so I could be wrong! >> >> IMO V4L is much better fit for this kind of devices than IIO. You can use just a >> subset of the API, it shouldn't take much effort to write a simple >> v4l2 capture driver, supporting fixed (probably vendor/chip specific) image >> format. I'm not sure if it's better to use the v4l2 controls [1], define a new >> v4l2 controls class for the fingerprint scanner processing features, rather than >> trying to pass raw data to user space and interpret it then in some library. I >> know there has been resistance to allowing passing unknown binary blobs to >> user space, due to possible abuses. >> >> [1] Documentation/video4linux/v4l2-controls.txt > > The fingerprint sensor acts more like a scanner device, so the closest type > is the V4L2_CAP_VIDEO_CAPTURE. However, this is not a perfect match because > the driver only sends an image, once, when triggered. Would it be a better > alternative to define a new capability type? Or it would be acceptable to > simply have a video device with no frame buffer or frame rate and the user > space application to read from the character device /dev/videoX? I don't think a new capability is needed for just one buffer capture. The capture driver could just support read() and signal it by setting the V4L2_CAP_READWRITE capability flag [2], [3]. [2] http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-querycap.html#device-capabilities [3] http://linuxtv.org/downloads/v4l-dvb-apis/io.html#rw -- Regards, Sylwester -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
