On Thu 2018-12-06 20:00:26, tristram...@microchip.com wrote: > > >>> Update tag_ksz.c to access switch driver's tail tagging operations. > > >> > > >> Hi Tristram > > >> > > >> Humm, i'm not sure we want this, the tagging spit into two places. I > > >> need to take a closer look at the previous patch, to see why it cannot > > >> be done here. > > > > > > O.K, i think i get what is going on. > > > > > > I would however implement it differently. > > > > > > One net/dsa/tag_X.c file can export two dsa_device_ops structures, > > > allowing you to share common code for the two taggers. You could call > > > these DSA_TAG_PROTO_KSZ_1_BYTE, and DSA_TAG_PROTO_KSZ_2_BYTE, > > and the > > > .get_tag_protocol call would then return the correct one for the > > > switch. > > > > Agreed, that is what is done by net/dsa/tag_brcm.c because there are two > > formats for the Broadcom tag: > > > > - TAG_BRCM: the 4-bytes Broadcom tag is between MAC SA and Ethertype > > - TAG_BRCM_PREPEND: the 4-bytes Broadcom tag is before the MAC DA > > > > I did try to implement this way. But the other switches do not have the same > format even though the length is the same. Then I need to change the > following > files for any new KSZ switch: include/linux/dsa.h, net/dsa/dsa.c, > net/dsa/dsa_priv.h, > and finally net/dsa/tag_ksz.c. > > Even then it will not work if Microchip wants to add 1588 PTP capability to > the switches. > > For KSZ9477 the length of the tail tag changes when the PTP function is > enabled. > Typically this function is either enabled or disabled all the time, but if > users want to > change that during normal operation to see how the switch behaves, the > transmit > function completely stops working correctly.
I'd be careful about locking. Seems like dsa was designed with "tag
format is static", and you want to change it dynamically...
Pavel
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