From owner-freebsd-usb@freebsd.org Mon Mar 2 21:51:24 2020 Return-Path: Delivered-To: freebsd-usb@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id C90F125B84F for ; Mon, 2 Mar 2020 21:51:24 +0000 (UTC) (envelope-from hps@selasky.org) Received: from mail.turbocat.net (turbocat.net [88.99.82.50]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) server-signature RSA-PSS (4096 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 48WYkL3gTWz4fKj for ; Mon, 2 Mar 2020 21:51:22 +0000 (UTC) (envelope-from hps@selasky.org) Received: from hps2020.home.selasky.org (unknown [62.141.129.235]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) by mail.turbocat.net (Postfix) with ESMTPSA id CAAC2260144; Mon, 2 Mar 2020 22:51:13 +0100 (CET) Subject: Re: Understanding how USB transmission works To: Farhan Khan , freebsd-usb@freebsd.org References: <8d84a572-f70f-4080-bfe2-263b7f97993c@www.fastmail.com> From: Hans Petter Selasky Message-ID: <497ed8b0-9d9b-8c35-74f5-e9fd2e32fc08@selasky.org> Date: Mon, 2 Mar 2020 22:48:38 +0100 User-Agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <8d84a572-f70f-4080-bfe2-263b7f97993c@www.fastmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 48WYkL3gTWz4fKj X-Spamd-Bar: ----- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=none; spf=pass (mx1.freebsd.org: domain of hps@selasky.org designates 88.99.82.50 as permitted sender) smtp.mailfrom=hps@selasky.org X-Spamd-Result: default: False [-5.42 / 15.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+a:mail.turbocat.net]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[selasky.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCPT_COUNT_TWO(0.00)[2]; IP_SCORE(-3.12)[ip: (-9.32), ipnet: 88.99.0.0/16(-4.71), asn: 24940(-1.56), country: DE(-0.02)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:24940, ipnet:88.99.0.0/16, country:DE]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2] X-BeenThere: freebsd-usb@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: FreeBSD support for USB List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 02 Mar 2020 21:51:24 -0000 On 2020-03-02 22:19, Farhan Khan wrote: > Hi all, > > I am trying to understand how FreeBSD's usb transfers work compared to OpenBSD by using the rum(4) driver. I am a little confused how the FreeBSD side works. In FreeBSD USB transfers are a statemachine. In the beginning you call the start method, and that invokes the statemachine callback in the SETUP state. There you setup all parameters, buffers, lengths etc. and then you can submit the USB transfer, which invoke the host controller drivers routines, which actually lay out the required DMA descriptors for data transfer. When the USB transfer is completed the statemachine callback is invoked again and you can choose what to do. --HPS > > On the OpenBSD side, it seems that after allocating the pipes, you use usbd_setup_xfer and usbd_transfer(). As an example, look at OpenBSD's /usr/src/sys/dev/usb/if_rum.c, starting on line 2027-2029, I believe that corresponds to FreeBSD's /usr/src/sys/dev/usb/wlan/if_rum.c, line 2607 (rum_setup_tx_list) which goes to 807. In this function, I see that it adds rum_tx_data (tx_data[i] to the end of tx_free. However, how does it actually send the data? I believe this occurs in the callback functions, specifically with the usbd_transfer_submit function, but I am not certain how that is triggered, especially when it is triggered by the driver, such as in a send function. > > Please assist. > Thank you! > > Links below to make it easy to follow: > OpenBSD: > https://github.com/openbsd/src/blob/2e342c845e9966c26657b08851237fc18e7b5ff5/sys/dev/usb/if_rum.c#L2024 > > FreeBSD: > 1. https://github.com/freebsd/freebsd/blob/499b2b565264824f2139ebcb5d1c97404a17e7e6/sys/dev/usb/wlan/if_rum.c#L2607 > 2. https://github.com/freebsd/freebsd/blob/499b2b565264824f2139ebcb5d1c97404a17e7e6/sys/dev/usb/wlan/if_rum.c#L807 > > -- > Farhan Khan > PGP Fingerprint: 1312 89CE 663E 1EB2 179C 1C83 C41D 2281 F8DA C0DE > > _______________________________________________ > freebsd-usb@freebsd.org mailing list > https://lists.freebsd.org/mailman/listinfo/freebsd-usb > To unsubscribe, send any mail to "freebsd-usb-unsubscribe@freebsd.org" >