Messages in this thread | | | Subject | Re: [Linux-kernel] [PATCH 2/4] usbnet: smsc95xx: align tx-buffer to word | From | Ben Hutchings <> | Date | Thu, 04 Oct 2018 17:53:16 +0100 |
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On Tue, 2018-10-02 at 10:26 +0100, Ben Dooks wrote: > The tegra driver requires alignment of the buffer, so try and > make this better by pushing the buffer start back to an word > aligned address. At the worst this makes memcpy() easier as > it is word aligned, at best it makes sure the usb can directly > map the buffer. > > Signed-off-by: Ben Dooks <ben.dooks@codethink.co.uk> > [todo - make this configurable] [...]
I don't think you need a separate kconfig symbol for this. Aligning RX buffers to words (or better, cache lines) is almost always a win, so long as the CPU can handle misaligned fields in the network/transport headers. You can use #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS to check that.
It seems like NET_IP_ALIGN should be defined to 0 or 2 depending on CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, but NET_IP_ALIGN predates the latter.
Ben.
-- Ben Hutchings, Software Developer Codethink Ltd https://www.codethink.co.uk/ Dale House, 35 Dale Street Manchester, M1 2HF, United Kingdom
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