Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757796AbaDWQC3 (ORCPT ); Wed, 23 Apr 2014 12:02:29 -0400 Received: from mail-pa0-f45.google.com ([209.85.220.45]:47978 "EHLO mail-pa0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757411AbaDWQCZ (ORCPT ); Wed, 23 Apr 2014 12:02:25 -0400 Date: Wed, 23 Apr 2014 09:02:21 -0700 From: Dmitry Torokhov To: Oliver Neukum Cc: Michal =?iso-8859-1?Q?Mal=FD?= , linux-input@vger.kernel.org, linux-kernel@vger.kernel.org, jkosina@suse.cz, elias.vds@gmail.com, anssi.hannula@iki.fi, simon@mungewell.org Subject: Re: [PATCH v2 11/24] input: Port hid-holtekff to ff-memless-next Message-ID: <20140423160220.GC10531@core.coreip.homeip.net> References: <1398175209-9565-1-git-send-email-madcatxster@devoid-pointer.net> <1398175209-9565-12-git-send-email-madcatxster@devoid-pointer.net> <1398255470.32091.3.camel@linux-fkkt.site> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1398255470.32091.3.camel@linux-fkkt.site> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Apr 23, 2014 at 02:17:50PM +0200, Oliver Neukum wrote: > On Tue, 2014-04-22 at 15:59 +0200, Michal Mal? wrote: > > static int holtekff_play(struct input_dev *dev, void *data, > > - struct ff_effect *effect) > > + const struct mlnx_effect_command *command) > > { > > struct hid_device *hid = input_get_drvdata(dev); > > struct holtekff_device *holtekff = data; > > + const struct mlnx_rumble_force *rumble_force = > > &command->u.rumble_force; > > int left, right; > > /* effect type 1, length 65535 msec */ > > u8 buf[HOLTEKFF_MSG_LENGTH] = > > { 0x01, 0x01, 0xff, 0xff, 0x10, 0xe0, 0x00 }; > > On the kernel stack. > > > > > - left = effect->u.rumble.strong_magnitude; > > - right = effect->u.rumble.weak_magnitude; > > - dbg_hid("called with 0x%04x 0x%04x\n", left, right); > > + switch (command->cmd) { > > + case MLNX_START_RUMBLE: > > + left = rumble_force->strong; > > + right = rumble_force->weak; > > + dbg_hid("called with 0x%04x 0x%04x\n", left, right); > > > > - if (!left && !right) { > > - holtekff_send(holtekff, hid, stop_all6); > > - return 0; > > - } > > + if (!left && !right) { > > + holtekff_send(holtekff, hid, stop_all6); > > + return 0; > > + } > > > > - if (left) > > - buf[1] |= 0x80; > > - if (right) > > - buf[1] |= 0x40; > > + if (left) > > + buf[1] |= 0x80; > > + if (right) > > + buf[1] |= 0x40; > > > > - /* The device takes a single magnitude, so we just sum them > > up. */ > > - buf[6] = min(0xf, (left >> 12) + (right >> 12)); > > + /* The device takes a single magnitude, so we just sum > > them up. */ > > + buf[6] = min(0xf, (left >> 12) + (right >> 12)); > > > > - holtekff_send(holtekff, hid, buf); > > - holtekff_send(holtekff, hid, start_effect_1); > > + holtekff_send(holtekff, hid, buf); > > + holtekff_send(holtekff, hid, start_effect_1); > > + return 0; > > + case MLNX_STOP_RUMBLE: > > + holtekff_send(holtekff, hid, stop_all6); > > + return 0; > > + default: > > + return -EINVAL; > > + } > > > > return 0; > > } > > This looks very much like doing DMA on the kernel stack. It isn't: static void holtekff_send(struct holtekff_device *holtekff, struct hid_device *hid, const u8 data[HOLTEKFF_MSG_LENGTH]) { int i; for (i = 0; i < HOLTEKFF_MSG_LENGTH; i++) { holtekff->field->value[i] = data[i]; } dbg_hid("sending %7ph\n", data); hid_hw_request(hid, holtekff->field->report, HID_REQ_SET_REPORT); } And also hid layer copies data a bunch of times over into DMA-safe buffers. > That is very strictly forbidden. The bug is also in the current > code, but would you care to fix it up? > > Regards > Oliver > > -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/