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Re: [PATCH v1 4/8] xen/riscv: introduce sbi call to putchar to console
- To: Bobby Eshleman <bobbyeshleman@xxxxxxxxx>, Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
- From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
- Date: Fri, 6 Jan 2023 17:16:31 +0000
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- Thread-topic: [PATCH v1 4/8] xen/riscv: introduce sbi call to putchar to console
On 20/12/2022 6:23 am, Bobby Eshleman wrote:
> On Fri, Jan 06, 2023 at 03:14:25PM +0200, Oleksii Kurochko wrote:
>> The patch introduce sbi_putchar() SBI call which is necessary
>> to implement initial early_printk
>>
> I think that it might be wise to start off with an alternative to
> sbi_putchar() since it is already planned for deprecation. I realize
> that this will require rework, but it is almost guaranteed that
> early_printk() will break on future SBI implementations if using this
> SBI call. IIRC, Xen/ARM's early printk looked like a reasonable analogy
> for how it could work on RISC-V, IMHO.
Hmm, we're using it as a stopgap right now in CI so we can break
"upstream RISC-V support" into manageable chunks.
So perhaps we want to forgo plumbing sbi_putchar() into early_printk()
(to avoid giving the impression that this will stay around in the
future) and use sbi_putchar() directly for the hello world print.
Next, we focus on getting the real uart driver working along with real
printk (rather than focusing on exceptions which was going to be the
next task), and we can drop sbi_putchar() entirely.
Thoughts?
~Andrew
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