modem: modem_cellular: Configurable MTU for CMUX #2661
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SeppoTakalo
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Allow configuring MTU for CMUX. Some AT manual and specification define this as a frame size. Linux ldattach default to 127 bytes, 3GPP TS 27.010 defaults to 31. We should limit our CMUX frames to a size that remote end is capable of handling. Linux silently drops oversized frames. Also, remove MODEM_CELLULAR_CMUX_MAX_FRAME_SIZE as this was only limiting a buffer sizes, and resulted CMUX frames to be capped to same value. Use MODEM_CMUX_WORK_BUFFER_SIZE and MODEM_CMUX_MTU instead. Also rename CONFIG_MODEM_CELLULAR_CHAT_BUFFER_SIZES to CONFIG_MODEM_CELLULAR_CHAT_BUFFER_SIZE as it is now only used as a Chat module. DLCI pipes use CONFIG_MODEM_CMUX_WORK_BUFFER_SIZE. Signed-off-by: Seppo Takalo <[email protected]> (cherry picked from commit c78081e)
If we end up writing zero bytes to cmux output, we can return zero instead of -ENOMEM as it would break various modules when using small buffers. For example modem_chat.c does not tolerate -ENOMEM but handles zero OK. Signed-off-by: Seppo Takalo <[email protected]> (cherry picked from commit 15b0f90)
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Can now be made a fromtree. |
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This is already changed to |
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Ah, nice. 🙂 Somehow didn't get a notification for the force push. |
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Pull in changes from zephyrproject-rtos/zephyr#87115
As the RC is approaching and the PR is slow to get in, I'll create a fromlist PR to get these changes into NCS for testing.
If the PR goes int before our RC, I'll refactor this to
[fromtree]