Hi Ayan,
On 03/12/2022 19:08, Ayan Kumar Halder wrote:
On 03/12/2022 18:05, Julien Grall wrote:
Hi Ayan,
Hi Julien,
Title: It suggests that this is modifying arch/arm whereas you are
updating the Arm part of the ns16550 driver.
In addition to that, from a reader PoV, it is more important to
emphase on the fact the truncation check is removed rather than the
extra assignment.
So I would suggest the following title:
xen/ns16550: Remove unneeded truncation check in the DT init code
Ack
On 01/12/2022 17:31, Ayan Kumar Halder wrote:
As "io_size" and "uart->io_size" are both u64, so there will be no
truncation.
Thus, one can remove the ASSERT() and extra assignment.
In an earlier commit (7c1de0038895cbc75ebd0caffc5b0f3f03c5ad51),
Please use 12-digit hash and provide the commit title.
Ack
"ns16550.io_size" was u32 and "io_size" was u64. Thus, the ASSERT()
was needed
to check if the values are the same.
However, in a later commit (c9f8e0aee507bec25104ca5535fde38efae6c6bc),
Ditto.
Ack
"ns16550.io_size" was changed to u64. Thus, the ASSERT() became
redundant.
Those two paragraphs explaining your reasoning why the truncation
check is removed. So I think they should be moved first. Then you can
add the initial paragraph to explain the resolution.
However... I wonder whether it would not be better to switch 'io_size'
to paddr_t because, as you said earlier one, on 32-bit ARMv8-R the
address is 32-bit. Therefore:
There are some more drivers where this kind of change (ie using paddr_t
instead of u64) is required. Thus, I wish to send it in a serie where I
will introduce CONFIG_ARM_PA_32 (to add support for 32 bit physical
addresses). Also ...
1. it sounds pointless to store the size using 64-bit
2. the truncation check still make sense (maybe hardened) in the
32-bit ARMv8-R to catch buggy DT.
Yes, but we need a common check for all the drivers/code as the DT gives
us 64 bit address (ie u64) and this needs to be translated to paddr_t
(which can be u64 or u32).
Again, as part of serie to introduce CONFIG_ARM_PA_32, I will provide
the following function to do address translation :-
That series is not on the ML and therefore I haven't had a chance to
fully review the outcome. So...
If you agree, I can send v2 with an updated commit message.
... I think it would be best if this patch is part of your upcoming series.
Cheers,
--
Julien Grall
