From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from lb3-smtp-cloud7.xs4all.net ([194.109.24.31]:51173 "EHLO lb3-smtp-cloud7.xs4all.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934178AbeCENvn (ORCPT ); Mon, 5 Mar 2018 08:51:43 -0500 From: Hans Verkuil To: linux-media@vger.kernel.org Cc: Wolfram Sang , Maxime Ripard , dri-devel@lists.freedesktop.org, Hans Verkuil Subject: [PATCHv2 6/7] cec-pin-error-inj.rst: document CEC Pin Error Injection Date: Mon, 5 Mar 2018 14:51:38 +0100 Message-Id: <20180305135139.95652-7-hverkuil@xs4all.nl> In-Reply-To: <20180305135139.95652-1-hverkuil@xs4all.nl> References: <20180305135139.95652-1-hverkuil@xs4all.nl> Sender: linux-media-owner@vger.kernel.org List-ID: From: Hans Verkuil The CEC Pin framework adds support for Error Injection. Document all the error injections commands and how to use it. Signed-off-by: Hans Verkuil --- .../media/cec-drivers/cec-pin-error-inj.rst | 322 +++++++++++++++++++++ Documentation/media/cec-drivers/index.rst | 1 + MAINTAINERS | 1 + 3 files changed, 324 insertions(+) create mode 100644 Documentation/media/cec-drivers/cec-pin-error-inj.rst diff --git a/Documentation/media/cec-drivers/cec-pin-error-inj.rst b/Documentation/media/cec-drivers/cec-pin-error-inj.rst new file mode 100644 index 000000000000..21bda831d3fb --- /dev/null +++ b/Documentation/media/cec-drivers/cec-pin-error-inj.rst @@ -0,0 +1,322 @@ +CEC Pin Framework Error Injection +================================= + +The CEC Pin Framework is a core CEC framework for CEC hardware that only +has low-level support for the CEC bus. Most hardware today will have +high-level CEC support where the hardware deals with driving the CEC bus, +but some older devices aren't that fancy. However, this framework also +allows you to connect the CEC pin to a GPIO on e.g. a Raspberry Pi and +you can become an instant CEC adapter. + +What makes doing this so interesting is that since we have full control +over the bus it is easy to support error injection. This is ideal to +test how well CEC adapters can handle error conditions. + +Currently only the cec-gpio driver (when the CEC line is directly +connected to a pull-up GPIO line) and the AllWinner A10/A20 drm driver +support this framework. + +If ``CONFIG_CEC_PIN_ERROR_INJ`` is enabled, then error injection is available +through debugfs. Specifically, in ``/sys/kernel/debug/cec/cecX/`` there is +now an ``error-inj`` file. + +With ``cat error-inj`` you can see both the possible commands and the current +error injection status: + +.. code-block:: none + + $ cat /sys/kernel/debug/cec/cec0/error-inj + # Clear error injections: + # clear clear all rx and tx error injections + # rx-clear clear all rx error injections + # tx-clear clear all tx error injections + # clear clear all rx and tx error injections for + # rx-clear clear all rx error injections for + # tx-clear clear all tx error injections for + # + # RX error injection: + # [,] rx-nack NACK the message instead of sending an ACK + # [,] rx-low-drive force a low-drive condition at this bit position + # [,] rx-add-byte add a spurious byte to the received CEC message + # [,] rx-remove-byte remove the last byte from the received CEC message + # [,] rx-arb-lost generate a POLL message to trigger an arbitration lost + # + # TX error injection settings: + # tx-ignore-nack-until-eom ignore early NACKs until EOM + # tx-custom-low-usecs define the 'low' time for the custom pulse + # tx-custom-high-usecs define the 'high' time for the custom pulse + # tx-custom-pulse transmit the custom pulse once the bus is idle + # + # TX error injection: + # [,] tx-no-eom don't set the EOM bit + # [,] tx-early-eom set the EOM bit one byte too soon + # [,] tx-add-bytes append (1-255) spurious bytes to the message + # [,] tx-remove-byte drop the last byte from the message + # [,] tx-short-bit make this bit shorter than allowed + # [,] tx-long-bit make this bit longer than allowed + # [,] tx-custom-bit send the custom pulse instead of this bit + # [,] tx-short-start send a start pulse that's too short + # [,] tx-long-start send a start pulse that's too long + # [,] tx-custom-start send the custom pulse instead of the start pulse + # [,] tx-last-bit stop sending after this bit + # [,] tx-low-drive force a low-drive condition at this bit position + # + # CEC message opcode (0-255) or 'any' + # 'once' (default), 'always', 'toggle' or 'off' + # CEC message bit (0-159) + # 10 bits per 'byte': bits 0-7: data, bit 8: EOM, bit 9: ACK + # CEC poll message used to test arbitration lost (0x00-0xff, default 0x0f) + # microseconds (0-10000000, default 1000) + + clear + +You can write error injection commands to ``error-inj`` using ``echo 'cmd' >error-inj`` +or ``cat cmd.txt >error-inj``. The ``cat error-inj`` output contains the current +error commands. You can save the output to a file and use it as an input to +``error-inj`` later. + +Basic Syntax +------------ + +Leading spaces/tabs are ignored. If the next character is a ``#`` or the end of the +line was reached, then the whole line is ignored. Otherwise a command is expected. + +The error injection commands fall in two main groups: those relating to receiving +CEC messages and those relating to transmitting CEC messages. In addition, there +are commands to clear existing error injection commands and to create custom +pulses on the CEC bus. + +Most error injection commands can be executed for specific CEC opcodes or for all +opcodes (``any``). Each command also has a 'mode' which can be ``off`` (can be used +to turn off an existing error injection command), ``once`` (the default) which will +trigger the error injection only once for the next received or transmitted message, +``always`` to always trigger the error injection and ``toggle`` to toggle the error +injection on or off for every transmit or receive. + +So '``any rx-nack``' will NACK the next received CEC message, '``any,always rx-nack``' will +NACK all received CEC messages and '``0x82,toggle rx-nack``' will only NACK if an Active +Source message was received and do that only for every other received message. + +After an error was injected with mode ``once`` the error injection command is cleared +automatically, so ``once`` is a one-time deal. + +All combinations of ```` and error injection commands can co-exist. So +this is fine: + +.. code-block:: none + + 0x9e tx-add-bytes 1 + 0x9e tx-early-eom + 0x9f tx-add-bytes 2 + any rx-nack + +All four error injection commands will be active simultaneously. + +However, if the same ```` and command combination is specified, +but with different arguments: + +.. code-block:: none + + 0x9e tx-add-bytes 1 + 0x9e tx-add-bytes 2 + +Then the second will overwrite the first. + +Clear Error Injections +---------------------- + +``clear`` + Clear all error injections. + +``rx-clear`` + Clear all receive error injections + +``tx-clear`` + Clear all transmit error injections + +`` clear`` + Clear all error injections for the given opcode. + +`` rx-clear`` + Clear all receive error injections for the given opcode. + +`` tx-clear`` + Clear all transmit error injections for the given opcode. + +Receive Messages +---------------- + +``[,] rx-nack`` + NACK broadcast messages and messages directed to this CEC adapter. + Every byte of the message will be NACKed in case the transmitter + keeps transmitting after the first byte was NACKed. + +``[,] rx-low-drive `` + Force a Low Drive condition at this bit position. If specifies + a specific CEC opcode then the bit position must be at least 18, + otherwise the opcode hasn't been received yet. This tests if the transmitter + can handle the Low Drive condition correctly and reports the error + correctly. Note that a Low Drive in the first 4 bits can also be + interpreted as an Arbitration Lost condition by the transmitter. + This is implementation dependent. + +``[,] rx-add-byte`` + Add a spurious 0x55 byte to the received CEC message, provided + the message was 15 bytes long or less. This is useful to test + the high-level protocol since spurious bytes should be ignored. + +``[,] rx-remove-byte`` + Remove the last byte from the received CEC message, provided it + was at least 2 bytes long. This is useful to test the high-level + protocol since messages that are too short should be ignored. + +``[,] rx-arb-lost `` + Generate a POLL message to trigger an Arbitration Lost condition. + This command is only allowed for ```` values of ``next`` or ``all``. + As soon as a start bit has been received the CEC adapter will switch + to transmit mode and it will transmit a POLL message. By default this is + 0x0f, but it can also be specified explicitly via the ```` argument. + + This command can be used to test the Arbitration Lost condition in + the remote CEC transmitter. Arbitration happens when two CEC adapters + start sending a message at the same time. In that case the initiator + with the most leading zeroes wins and the other transmitter has to + stop transmitting ('Arbitration Lost'). This is very hard to test, + except by using this error injection command. + + This does not work if the remote CEC transmitter has logical address + 0 ('TV') since that will always win. + +Transmit Messages +----------------- + +``tx-ignore-nack-until-eom`` + This setting changes the behavior of transmitting CEC messages. Normally + as soon as the receiver NACKs a byte the transmit will stop, but the + specification also allows that the full message is transmitted and only + at the end will the transmitter look at the ACK bit. This is not recommended + behavior since there is no point in keeping the CEC bus busy for longer than + is strictly needed. Especially given how slow the bus is. + + This setting can be used to test how well a receiver deals with transmitters + that ignore NACKs until the very end of the message. + +``[,] tx-no-eom`` + Don't set the EOM bit. Normally the last byte of the message has the EOM + (End-Of-Message) bit set. With this command the transmit will just stop + without ever sending an EOM. This can be used to test how a receiver + handles this case. Normally receivers have a time-out after which + they will go back to the Idle state. + +``[,] tx-early-eom`` + Set the EOM bit one byte too soon. This obviously only works for messages + of two bytes or more. The EOM bit will be set for the second-to-last byte + and not for the final byte. The receiver should ignore the last byte in this + case. Since the resulting message is likely to be too short for this same + reason the whole message is typically ignored. The receiver should be in + Idle state after the last byte was transmitted. + +``[,] tx-add-bytes `` + Append ```` (1-255) spurious bytes to the message. The extra bytes + have the value of the byte position in the message. So if you transmit a + two byte message (e.g. a Get CEC Version message) and add 2 bytes, then + the full message received by the remote CEC adapter is ``0x40 0x9f 0x02 0x03``. + + This command can be used to test buffer overflows in the receiver. E.g. + what does it do when it receives more than the maximum message size of 16 + bytes. + +``[,] tx-remove-byte`` + Drop the last byte from the message, provided the message is at least + two bytes long. The receiver should ignore messages that are too short. + +``[,] tx-short-bit `` + Make this bit period shorter than allowed. The bit position cannot be + an Ack bit. If specifies a specific CEC opcode then the bit position + must be at least 18, otherwise the opcode hasn't been received yet. Normally the + period of a data bit is between 2.05 and 2.75 milliseconds. With this + command the period of this bit is 1.8 milliseconds, this is done by + reducing the time the CEC bus is high. This bit period is less than + is allowed and the receiver should respond with a Low Drive + condition. + + This command is ignored for 0 bits in bit positions 0 to 3. This is + because the receiver also looks for an Arbitration Lost condition in + those first four bits and it is undefined what will happen if it + sees a too-short 0 bit. + +``[,] tx-long-bit `` + Make this bit period longer than is valid. The bit position cannot be + an Ack bit. If specifies a specific CEC opcode then the bit position + must be at least 18, otherwise the opcode hasn't been received yet. Normally the + period of a data bit is between 2.05 and 2.75 milliseconds. With this + command the period of this bit is 2.9 milliseconds, this is done by + increasing the time the CEC bus is high. + + Even though this bit period is longer than is valid it is undefined what + a receiver will do. It might just accept it, or it might time out and + return to Idle state. Unfortunately the CEC specification is silent about + this. + + This command is ignored for 0 bits in bit positions 0 to 3. This is + because the receiver also looks for an Arbitration Lost condition in + those first four bits and it is undefined what will happen if it + sees a too-long 0 bit. + +``[,] tx-short-start`` + Make this start bit period shorter than allowed. Normally the period of a start bit is + between 4.3 and 4.7 milliseconds. With this command the period of the + start bit is 4.1 milliseconds, this is done by reducing the time the + CEC bus is high. This start bit period is less than is allowed + and the receiver should return to Idle state when this is detected. + +``[,] tx-long-start`` + Make this start bit period longer than is valid. Normally the period of a start bit is + between 4.3 and 4.7 milliseconds. With this command the period of the + start bit is 5 milliseconds, this is done by increasing the time the + CEC bus is high. This start bit period is more than is valid + and the receiver should return to Idle state when this is detected. + + Even though this start bit period is longer than is valid it is undefined what + a receiver will do. It might just accept it, or it might time out and + return to Idle state. Unfortunately the CEC specification is silent about + this. + +``[,] tx-last-bit `` + Just stop transmitting after this bit. If specifies a specific CEC + opcode then the bit position must be at least 18, otherwise the opcode + hasn't been received yet. This command can be used to test how the receiver reacts + when a message just suddenly stops. It should time out and go back to Idle + state. + +``[,] tx-low-drive `` + Force a Low Drive condition at this bit position. If specifies a specific + CEC opcode then the bit position must be at least 18, otherwise the opcode + hasn't been received yet. This can be used to test how the receiver handles Low Drive + conditions. Note that if this happens at bit positions 0-3 the receiver + can interpret this as an Arbitration Lost condition. This is implementation + dependent. + +Custom Pulses +------------- + +``tx-custom-low-usecs `` + This defines the duration in microseconds that the custom pulse pulls the CEC line low. + The default is 1000 microseconds. + +``tx-custom-high-usecs `` + This defines the duration in microseconds that the custom pulse keeps the + CEC line high (unless another CEC adapter pulls it low in that time). + The default is 1000 microseconds. The total period of the custom pulse is + ``tx-custom-low-usecs + tx-custom-high-usecs``. + +``[,] tx-custom-bit `` + Send the custom bit instead of a regular data bit. The bit position cannot be + an Ack bit. If specifies a specific CEC opcode then the bit position + must be at least 18, otherwise the opcode hasn't been received yet. + +``[,] tx-custom-start`` + Send the custom bit instead of a regular start bit. + +``tx-custom-pulse`` + Transmit a single custom pulse as soon as the CEC bus is idle. diff --git a/Documentation/media/cec-drivers/index.rst b/Documentation/media/cec-drivers/index.rst index 7ef204823422..3580bdb790bc 100644 --- a/Documentation/media/cec-drivers/index.rst +++ b/Documentation/media/cec-drivers/index.rst @@ -31,4 +31,5 @@ For more details see the file COPYING in the source distribution of Linux. :maxdepth: 5 :numbered: + cec-pin-error-inj pulse8-cec diff --git a/MAINTAINERS b/MAINTAINERS index 91ed6adfa4a6..085b40adbe4d 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3305,6 +3305,7 @@ F: include/media/cec-notifier.h F: include/uapi/linux/cec.h F: include/uapi/linux/cec-funcs.h F: Documentation/devicetree/bindings/media/cec.txt +F: Documentation/media/cec-drivers/cec-pin-error-inj.rst CEC GPIO DRIVER M: Hans Verkuil -- 2.16.1