net: caif: Remove unused caif SPI driver

While chasing in_interrupt() (ab)use in drivers it turned out that the
caif_spi driver has never been in use since the driver was merged 10 years
ago. There never was any matching code which provides a platform device.

The driver has not seen any update (asided of treewide changes and
cleanups) since 8 years and the maintainers vanished from the planet.

So analysing the potential contexts and the (in)correctness of
in_interrupt() usage is just a pointless exercise.

Remove the cruft.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 0 insertions, 230 deletions

diff --git a/Documentation/networking/caif/index.rst b/Documentation/networking/caif/index.rst
index 86e5b7832ec3..ec29b6f4bdb4 100644
--- a/Documentation/networking/caif/index.rst
+++ b/Documentation/networking/caif/index.rst
@@ -10,4 +10,3 @@ Contents:
 
    linux_caif
    caif
-   spi_porting
diff --git a/Documentation/networking/caif/spi_porting.rst b/Documentation/networking/caif/spi_porting.rst
deleted file mode 100644
index d49f874b20ac..000000000000
--- a/Documentation/networking/caif/spi_porting.rst
+++ /dev/null
@@ -1,229 +0,0 @@
-.. SPDX-License-Identifier: GPL-2.0
-
-================
-CAIF SPI porting
-================
-
-CAIF SPI basics
-===============
-
-Running CAIF over SPI needs some extra setup, owing to the nature of SPI.
-Two extra GPIOs have been added in order to negotiate the transfers
-between the master and the slave. The minimum requirement for running
-CAIF over SPI is a SPI slave chip and two GPIOs (more details below).
-Please note that running as a slave implies that you need to keep up
-with the master clock. An overrun or underrun event is fatal.
-
-CAIF SPI framework
-==================
-
-To make porting as easy as possible, the CAIF SPI has been divided in
-two parts. The first part (called the interface part) deals with all
-generic functionality such as length framing, SPI frame negotiation
-and SPI frame delivery and transmission. The other part is the CAIF
-SPI slave device part, which is the module that you have to write if
-you want to run SPI CAIF on a new hardware. This part takes care of
-the physical hardware, both with regard to SPI and to GPIOs.
-
-- Implementing a CAIF SPI device:
-
-	- Functionality provided by the CAIF SPI slave device:
-
-	In order to implement a SPI device you will, as a minimum,
-	need to implement the following
-	functions:
-
-	::
-
-	    int (*init_xfer) (struct cfspi_xfer * xfer, struct cfspi_dev *dev):
-
-	This function is called by the CAIF SPI interface to give
-	you a chance to set up your hardware to be ready to receive
-	a stream of data from the master. The xfer structure contains
-	both physical and logical addresses, as well as the total length
-	of the transfer in both directions.The dev parameter can be used
-	to map to different CAIF SPI slave devices.
-
-	::
-
-	    void (*sig_xfer) (bool xfer, struct cfspi_dev *dev):
-
-	This function is called by the CAIF SPI interface when the output
-	(SPI_INT) GPIO needs to change state. The boolean value of the xfer
-	variable indicates whether the GPIO should be asserted (HIGH) or
-	deasserted (LOW). The dev parameter can be used to map to different CAIF
-	SPI slave devices.
-
-	- Functionality provided by the CAIF SPI interface:
-
-	::
-
-	    void (*ss_cb) (bool assert, struct cfspi_ifc *ifc);
-
-	This function is called by the CAIF SPI slave device in order to
-	signal a change of state of the input GPIO (SS) to the interface.
-	Only active edges are mandatory to be reported.
-	This function can be called from IRQ context (recommended in order
-	not to introduce latency). The ifc parameter should be the pointer
-	returned from the platform probe function in the SPI device structure.
-
-	::
-
-	    void (*xfer_done_cb) (struct cfspi_ifc *ifc);
-
-	This function is called by the CAIF SPI slave device in order to
-	report that a transfer is completed. This function should only be
-	called once both the transmission and the reception are completed.
-	This function can be called from IRQ context (recommended in order
-	not to introduce latency). The ifc parameter should be the pointer
-	returned from the platform probe function in the SPI device structure.
-
-	- Connecting the bits and pieces:
-
-		- Filling in the SPI slave device structure:
-
-		  Connect the necessary callback functions.
-
-		  Indicate clock speed (used to calculate toggle delays).
-
-		  Chose a suitable name (helps debugging if you use several CAIF
-		  SPI slave devices).
-
-		  Assign your private data (can be used to map to your
-		  structure).
-
-		- Filling in the SPI slave platform device structure:
-
-		  Add name of driver to connect to ("cfspi_sspi").
-
-		  Assign the SPI slave device structure as platform data.
-
-Padding
-=======
-
-In order to optimize throughput, a number of SPI padding options are provided.
-Padding can be enabled independently for uplink and downlink transfers.
-Padding can be enabled for the head, the tail and for the total frame size.
-The padding needs to be correctly configured on both sides of the link.
-The padding can be changed via module parameters in cfspi_sspi.c or via
-the sysfs directory of the cfspi_sspi driver (before device registration).
-
-- CAIF SPI device template::
-
-    /*
-    *	Copyright (C) ST-Ericsson AB 2010
-    *	Author: Daniel Martensson / Daniel.Martensson@stericsson.com
-    *	License terms: GNU General Public License (GPL), version 2.
-    *
-    */
-
-    #include <linux/init.h>
-    #include <linux/module.h>
-    #include <linux/device.h>
-    #include <linux/wait.h>
-    #include <linux/interrupt.h>
-    #include <linux/dma-mapping.h>
-    #include <net/caif/caif_spi.h>
-
-    MODULE_LICENSE("GPL");
-
-    struct sspi_struct {
-	    struct cfspi_dev sdev;
-	    struct cfspi_xfer *xfer;
-    };
-
-    static struct sspi_struct slave;
-    static struct platform_device slave_device;
-
-    static irqreturn_t sspi_irq(int irq, void *arg)
-    {
-	    /* You only need to trigger on an edge to the active state of the
-	    * SS signal. Once a edge is detected, the ss_cb() function should be
-	    * called with the parameter assert set to true. It is OK
-	    * (and even advised) to call the ss_cb() function in IRQ context in
-	    * order not to add any delay. */
-
-	    return IRQ_HANDLED;
-    }
-
-    static void sspi_complete(void *context)
-    {
-	    /* Normally the DMA or the SPI framework will call you back
-	    * in something similar to this. The only thing you need to
-	    * do is to call the xfer_done_cb() function, providing the pointer
-	    * to the CAIF SPI interface. It is OK to call this function
-	    * from IRQ context. */
-    }
-
-    static int sspi_init_xfer(struct cfspi_xfer *xfer, struct cfspi_dev *dev)
-    {
-	    /* Store transfer info. For a normal implementation you should
-	    * set up your DMA here and make sure that you are ready to
-	    * receive the data from the master SPI. */
-
-	    struct sspi_struct *sspi = (struct sspi_struct *)dev->priv;
-
-	    sspi->xfer = xfer;
-
-	    return 0;
-    }
-
-    void sspi_sig_xfer(bool xfer, struct cfspi_dev *dev)
-    {
-	    /* If xfer is true then you should assert the SPI_INT to indicate to
-	    * the master that you are ready to receive the data from the master
-	    * SPI. If xfer is false then you should de-assert SPI_INT to indicate
-	    * that the transfer is done.
-	    */
-
-	    struct sspi_struct *sspi = (struct sspi_struct *)dev->priv;
-    }
-
-    static void sspi_release(struct device *dev)
-    {
-	    /*
-	    * Here you should release your SPI device resources.
-	    */
-    }
-
-    static int __init sspi_init(void)
-    {
-	    /* Here you should initialize your SPI device by providing the
-	    * necessary functions, clock speed, name and private data. Once
-	    * done, you can register your device with the
-	    * platform_device_register() function. This function will return
-	    * with the CAIF SPI interface initialized. This is probably also
-	    * the place where you should set up your GPIOs, interrupts and SPI
-	    * resources. */
-
-	    int res = 0;
-
-	    /* Initialize slave device. */
-	    slave.sdev.init_xfer = sspi_init_xfer;
-	    slave.sdev.sig_xfer = sspi_sig_xfer;
-	    slave.sdev.clk_mhz = 13;
-	    slave.sdev.priv = &slave;
-	    slave.sdev.name = "spi_sspi";
-	    slave_device.dev.release = sspi_release;
-
-	    /* Initialize platform device. */
-	    slave_device.name = "cfspi_sspi";
-	    slave_device.dev.platform_data = &slave.sdev;
-
-	    /* Register platform device. */
-	    res = platform_device_register(&slave_device);
-	    if (res) {
-		    printk(KERN_WARNING "sspi_init: failed to register dev.\n");
-		    return -ENODEV;
-	    }
-
-	    return res;
-    }
-
-    static void __exit sspi_exit(void)
-    {
-	    platform_device_del(&slave_device);
-    }
-
-    module_init(sspi_init);
-    module_exit(sspi_exit);