From: Michal Pecio <michal.pecio@gmail.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Brent Page <brentfpage@gmail.com>, linux-usb@vger.kernel.org
Subject: Re: TT budgeting for EHCI; accommodate 1023-byte full-speed isochronous–in endpoints
Date: Wed, 29 Apr 2026 13:58:28 +0200 [thread overview]
Message-ID: <20260429135828.3e7f0675.michal.pecio@gmail.com> (raw)
In-Reply-To: <20260429113604.2204b646.michal.pecio@gmail.com>
On Wed, 29 Apr 2026 11:36:04 +0200, Michal Pecio wrote:
> The host must schedule SSPLITs assuming no bit-stuffing to prevent TT
> buffer underrun on long OUT packets. Assuming minimum/no packet headers
> further minimizes downstream idle. TTs are required to buffer this.
>
> (BTW, periodic transfers should occur before async. Could the TT run
> out of periodic, do async, then get an unexpected periodic transaction
> in the next uframe? What happens?)
>
> Including packet headers for SSPLIT scheduling seems harmless unless
> overestimated, but apparently it's not required. TTs must cope.
Or maybe not, because 11.18.2 states that "budgeting" includes packet
overhead and think time. And TT must handle gaps in periodic schedule
due to short transfers and deal with not knowing whether there will be
periodic transfers in the next uframe till the last moment.
next prev parent reply other threads:[~2026-04-29 11:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-04-28 1:24 TT budgeting for EHCI; accommodate 1023-byte full-speed isochronous–in endpoints Brent Page
2026-04-28 21:19 ` Alan Stern
2026-04-29 9:36 ` Michal Pecio
2026-04-29 11:58 ` Michal Pecio [this message]
2026-04-29 17:56 ` Alan Stern
2026-04-29 19:24 ` Michal Pecio
2026-04-29 19:32 ` Alan Stern
2026-04-29 19:52 ` Brent Page
2026-04-30 2:27 ` Alan Stern
2026-04-30 6:46 ` Brent Page
2026-04-29 20:04 ` Michal Pecio
2026-04-30 1:47 ` Alan Stern
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