On Tue, Oct 25, 2016 at 07:38:55AM +0200, LABBE Corentin wrote: > On Mon, Oct 24, 2016 at 10:10:20PM +0200, Maxime Ripard wrote: > > On Sat, Oct 22, 2016 at 03:53:28PM +0200, Corentin Labbe wrote: > > > Since SID's content is constant over reboot, > > > > That's not true, at least not across all the Allwinner SoCs, and > > especially not on the A10 and A20 that this driver supports. > > > > On my cubieboard2 (A20) > hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur| > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur| > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > 00000200 > cubiedev ~ # reboot > cubiedev ~ # hexdump -C /sys/devices/platform/soc\@01c00000/1c23800.eeprom/sunxi-sid0/nvmem > 00000000 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur| > 00000010 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > 00000100 16 51 66 83 80 48 50 72 56 54 48 48 03 c2 75 72 |.Qf..HPrVTHH..ur| > 00000110 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................| > * > 00000200 > > So clearly for me its constant. It's constant across reboots, but not across devices. Each device have a different SID content, therefore it's a relevant source of entropy in the system. Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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