|
This isn't strictly embedded Linux but it's an embedded project so I'll try here anyways. I have a user-land application that I want to block on a sysfs file that only returns when data (any data) is written to that file. This will signal that the user application can continue on it's way. I'm not sure how to do this easily. I created a sysfs attribute in my kernel driver and tried calling sysfs_notify() in the "store" routine of my attribute which should signal to the poll() routine my user application is blocking on, but poll always returns instantly with the event POLLIN as the return event. I tried switching the poll event to POLLPRI and it does block but never returns even after hitting sysfs_notify in the kernel "store" routine. I can see with mesgd that both my "show" and "store" routines of the kernel attribute are being hit by my user-land application. Any thoughts what I might be doing wrong? I'm also open to trying a different method than poll, I don't actually care about the data being written to the sysfs file I just need to use it as a signal to my application.
|
#
¿
Oct 3, 2016 05:31
|
|
|
|
| # ¿ May 16, 2024 20:27 |
|
|
Minus Pants posted:How'd you get into/learn board layout? I've had some simple low freq boards made, but I haven't found many good, practical resources for common high-speed signal routing (USB, SATA, memory, etc.). Also, what's your verification workflow like (test gear, software, lessons learned)? As someone who dabbles in board layout but is primarily a firmware guy. Take a look at datasheets for the ICs you plant to use, they usually have a reference layout section that is very useful. Also find a board online that is doing something similiar to what you want to do and look up it's schematic. Something like laying out DDR lines is obviously a lot more sensitive but there are guidelines out there. My main problem is that even when I have an example schematic I want to use that tells me capacitor/inductor/resistor values for a part I don't know what type to use. For example how do I decide to use ceramic/tantalum/film?
|
|
#
¿
Oct 3, 2016 05:36
|
|
|
How many MIPI lanes are you using? I had a project awhile back with two displays on an i.MX6 that used both the direct MIPI interface (2 lanes) to the i.MX and then a 4 lane MIPI interface display that was connected via the i.MX LVDS interface to a LVDS/MIPI bridge and then to the display. I never quite got the bridge interface to work but the 2 lane direct MIPI interface was fairly straightforward.
|
|
#
¿
Dec 10, 2016 07:45
|
|
|
Use Yocto if you enjoy layers and layers of confusion and complexity.
|
|
#
¿
Jul 16, 2017 18:11
|
|