Date: Wed, 20 Apr 2022 12:34:02 +0000 From: "Brian McGovern (bmcgover)" <bmcgover@cisco.com> To: Chris Hill <chris@monochrome.org> Cc: "freebsd-questions@freebsd.org" <freebsd-questions@freebsd.org> Subject: Re: Number of USB devices limited? Message-ID: <BL1PR11MB55096D7496B9E6449ACD6B89C5F59@BL1PR11MB5509.namprd11.prod.outlook.com> In-Reply-To: <alpine.BSF.2.20.2204192304410.2458@tripel.monochrome.org> References: <BL1PR11MB550957CB5932655D66799676C5F29@BL1PR11MB5509.namprd11.prod.outlook.com> <alpine.BSF.2.20.2204192304410.2458@tripel.monochrome.org>
next in thread | previous in thread | raw e-mail | index | archive | help
--_000_BL1PR11MB55096D7496B9E6449ACD6B89C5F59BL1PR11MB5509namp_
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
> Not specific to FreeBSD, but to the USB standard itself (I think). There =
is a limit to the number of endpoints, as you describe, but there is also a=
limit to the number of > hubs you can cascade. The number is low; I think =
it's 7. If you have more than $NUMBER of hubs in a row, you will get errati=
c behavior from your USB endpoints. And
> many things count as a "hub" - your computer probably takes up two, for e=
xample.
Thanks. I'll take a look when I get online and see if I can figure out what=
the hub[s] is[are] adding to the overhead.
-Brian
________________________________
From: Chris Hill <chris@monochrome.org>
Sent: Tuesday, April 19, 2022 11:09 PM
To: Brian McGovern (bmcgover) <bmcgover@cisco.com>
Cc: freebsd-questions@freebsd.org <freebsd-questions@freebsd.org>
Subject: Re: Number of USB devices limited?
Not specific to FreeBSD, but to the USB standard itself (I think). There
is a limit to the number of endpoints, as you describe, but there is
also a limit to the number of hubs you can cascade. The number is low; I
think it's 7. If you have more than $NUMBER of hubs in a row, you will
get erratic behavior from your USB endpoints. And many things count as a
"hub" - your computer probably takes up two, for example.
On Tue, 19 Apr 2022, Brian McGovern (bmcgover) wrote:
> Looking at the FreeBSD handbook, Chapter 13, it looks like the
> expectation is that I should be able to attach "the maximum of 126
> devices". Unfortunately, it seems I'm getting in the low 20s (21 FTDI
> serial cables, USB keyboard, and mouse), after which I start getting
> the following in the logs:
>
> "Error initializing deviceusb_alloc_device: device init 34 failed
> (USB_ERR_IOERROR, ignored)"
>
> and
>
> "uhub_reattach_port: could not allocate new device".
>
>
> If I look at /dev/ugen*, there are the ugen devices for 0.1->0.33; so
> its feeling like there may be limit in the serial port driver for the
> number of /dev/cua* devices, which presently only number
> cuaU0->cuaU20. So, I'm assuming this may not be a "USB" issue as much
> as the number of USB serial ports (ucom?) that can be connected.
>
> Before I go on a code crawl to figure out how this is failing and if
> it can be scaled up, I'm curious if anyone is aware of a coded limit
> for the number of USB serial devices (or USB devices in general) that
> can be connected before running in to this? I'm looking to push
> upwards to _maybe_ 40 FTDI devices.
>
> -Brian
>
--
Chris Hill chris@monochrome.org
--_000_BL1PR11MB55096D7496B9E6449ACD6B89C5F59BL1PR11MB5509namp_
Content-Type: text/html; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
<html>
<head>
<meta http-equiv=3D"Content-Type" content=3D"text/html; charset=3Dus-ascii"=
>
<style type=3D"text/css" style=3D"display:none;"> P {margin-top:0;margin-bo=
ttom:0;} </style>
</head>
<body dir=3D"ltr">
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<font size=3D"2"><span style=3D"font-size:11pt">> Not specific to FreeBS=
D, but to the USB standard itself (I think). There is a limit to the number=
of endpoints, as you describe, but there is also a limit to the number of =
> hubs you can cascade. The number is low;
I think it's 7. If you have more than $NUMBER of hubs in a row, you will g=
et erratic behavior from your USB endpoints. And
<br>
</span></font></div>
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<font size=3D"2"><span style=3D"font-size:11pt">> many things count as a=
"hub" - your computer probably takes up two, for example.</span>=
</font></div>
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<font size=3D"2">Thanks. I'll take a look when I get online and see if I ca=
n figure out what the hub[s] is[are] adding to the overhead.
<br>
</font></div>
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<br>
</div>
<div style=3D"font-family: Calibri, Arial, Helvetica, sans-serif; font-size=
: 12pt; color: rgb(0, 0, 0);">
<font size=3D"2"> &nbs=
p; -Brian</font><br>
</div>
<div id=3D"appendonsend"></div>
<hr style=3D"display:inline-block;width:98%" tabindex=3D"-1">
<div id=3D"divRplyFwdMsg" dir=3D"ltr"><font face=3D"Calibri, sans-serif" st=
yle=3D"font-size:11pt" color=3D"#000000"><b>From:</b> Chris Hill <chris@=
monochrome.org><br>
<b>Sent:</b> Tuesday, April 19, 2022 11:09 PM<br>
<b>To:</b> Brian McGovern (bmcgover) <bmcgover@cisco.com><br>
<b>Cc:</b> freebsd-questions@freebsd.org <freebsd-questions@freebsd.org&=
gt;<br>
<b>Subject:</b> Re: Number of USB devices limited?</font>
<div> </div>
</div>
<div class=3D"BodyFragment"><font size=3D"2"><span style=3D"font-size:11pt;=
">
<div class=3D"PlainText">Not specific to FreeBSD, but to the USB standard i=
tself (I think). There
<br>
is a limit to the number of endpoints, as you describe, but there is <br>
also a limit to the number of hubs you can cascade. The number is low; I <b=
r>
think it's 7. If you have more than $NUMBER of hubs in a row, you will <br>
get erratic behavior from your USB endpoints. And many things count as a <b=
r>
"hub" - your computer probably takes up two, for example.<br>
<br>
<br>
On Tue, 19 Apr 2022, Brian McGovern (bmcgover) wrote:<br>
<br>
> Looking at the FreeBSD handbook, Chapter 13, it looks like the <br>
> expectation is that I should be able to attach "the maximum of 12=
6 <br>
> devices". Unfortunately, it seems I'm getting in the low 20s (21 =
FTDI <br>
> serial cables, USB keyboard, and mouse), after which I start getting <=
br>
> the following in the logs:<br>
><br>
> "Error initializing deviceusb_alloc_device: device init 34 failed=
<br>
> (USB_ERR_IOERROR, ignored)"<br>
><br>
> and<br>
><br>
> "uhub_reattach_port: could not allocate new device".<br>
><br>
><br>
> If I look at /dev/ugen*, there are the ugen devices for 0.1->0.33; =
so <br>
> its feeling like there may be limit in the serial port driver for the =
<br>
> number of /dev/cua* devices, which presently only number <br>
> cuaU0->cuaU20. So, I'm assuming this may not be a "USB" i=
ssue as much <br>
> as the number of USB serial ports (ucom?) that can be connected.<br>
><br>
> Before I go on a code crawl to figure out how this is failing and if <=
br>
> it can be scaled up, I'm curious if anyone is aware of a coded limit <=
br>
> for the number of USB serial devices (or USB devices in general) that =
<br>
> can be connected before running in to this? I'm looking to push <br>
> upwards to _maybe_ 40 FTDI devices.<br>
><br>
> -Brian<br>
><br>
<br>
-- <br>
Chris Hill  =
; chris@monochrome.org<br>
</div>
</span></font></div>
</body>
</html>
--_000_BL1PR11MB55096D7496B9E6449ACD6B89C5F59BL1PR11MB5509namp_--
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?BL1PR11MB55096D7496B9E6449ACD6B89C5F59>